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Ascites in Broilers.
Ascites in Broilers. 1. Experimental Factors Evoking Symptoms Related to Ascites C. W. SCHEELE, W. DE WIT, M. T. FRANKENHUIS,1 and P.F.G. VEREIJKEN2 Spelderholt Centre for Poultry Research and Information Services, 7361 DA Beekbergen, The Netherlands (Received for publication July 31, 1990)
1991 Poultry Science 70:1069-1083 INTRODUCTION
Ascites refers to the accumulation of edematous fluid within the abdominal cavity. This disease is related to other symptoms having the collective name of "heart failure syndrome" (HFS). Heart failure syndrome comprises abnormalities such as hypertrophy of the heart, especially of the right ventricle, dilation of the heart and hydropericardium, and congested and edematous lungs, as was found by Olander et al. (1967) and Burton et al. (1968). Van der Hel et al. (1988) showed that pathogenic abnormalities in hypoxic broilers exposed to a decreased partial oxygen pressure of 152 millibar (mb) were comparable with those related to ascites, observed in Dutch poultry farms. Huchzermeyer (1984) and Julian (1987) mentioned various factors and agents which contribute to the occurrence of aggravation of ascites and HFS such as salt in feed, furazolidone, plant poisons, and other toxins affecting blood pressure and function of liver, heart, and lungs. Studies concerning the relationship
Royal Zoological Society, Natura Artis Magistra, Amsterdam, The Netherlands. Agricultural Mathematics Group, Wageningen, The Netherlands.
between low partial oxygen pressures at high altitudes and "high altitude disease" provide background data on conditions leading to the development of heart failure and ascites in birds. Generally, avian species are more tolerant to high altitudes than are mammalian species (Schmidt-Nielsen, 1983). Domestic poultry are an exception. Atland (1961) found that chickens had a much lower altitude tolerance than other small warm-blooded animals previously studied. Low partial oxygen pressures resulting in oxygen deficiency or hypoxia leads to tissue oxygen deprivation or anoxia. The low hypoxia resistance of chickens is related to their relatively low hematocrit values, low oxygen-carrying capacity (Rostorfer and Rigdon, 1947), and to the inefficient oxygenation of the fowl lung (Sykes, 1960). Grover et al. (1983) found in an isolated rat lung that acute and chronic hypoxia had an important influence on pulmonary vasomotor tone. Regional reductions in alveolar O2 tension constricted the nearby arterioles. This prevented the return of poorly oxygenated blood to the left atrium by exploiting primarily the better ventilated alveoli. The same adjustment of the regional pulmonary circulation to differences in oxygen tension was found in the duck by Scheid and Holle (1978). Li such a
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ABSTRACT Male broilers of two genetically related stocks with divergent growth rates and feed conversion ratios were used to study metabolic backgrounds on the occurrence of pulmonary hypertension, heart failure, hypoxemia, and ascites in poultry. An experiment with a 2 x 2 x 2 x 2 factorial split-plot arrangement of treatments with 96 groups of 12 broilers was performed. Effects of stock and environmental factors such as ambient temperature, dietary fat, and dietary energy on performance, energy metabolism, oxygen consumption, hematocrit values, and mortality were investigated in broilers from 1 to 5 wk of age. Dissimilar responses of the two stocks to environmental factors reflected genotype by environment interactions and revealed metabolic disorders related to heart failure and ascites. The results indicated that in the stock with the lower feed conversion ratio, a fast protein accretion was achieved together with a reduced ability to convert chemical energy to metabolic heat and to deposit body fat directly from ingested fat Birds with a low feed conversion ratio show less flexibility in metabolic adaptation to a changing environment, which can account for the development of ascites. {Key words: broiler strains, metabolism, feed conversion ratio, dietary factors, ascites)
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incidence of high altitude disease, resulting in pulmonary arterial hypertension, right ventricular hypertrophy, heart failure, hydropericardium, edema in lungs, and ascites in mammals and birds was described by Alexander et al. (1960), Burton et al. (1968), Cueva et al. (1974), and Sillau et al. (1980). More recently, similar symptoms with high mortality rates were observed in broilers at altitudes lower than 2,000 m (Van Blerk, 1985) and even at sea level (Julian et al., 1987; 1989; Scheele and Frankenhuis, 1989). These studies indicated that factors other than a decreased oxygen pressure can create hypoxic conditions in fast-growing meat-type chickens. A low environmental temperature, stimulating the metabolic rate and causing an increased oxygen requirement, had a marked effect on the incidence of HFS and ascites. Julian et al. (1987) indicated that rapidly growing broilers are more susceptible to increased pulmonary arterial pressure than slowly growing broilers. Fast-growing chickens might exhibit elevated metabolic rates and a faster blood flow together with higher oxygen requirements. As a result, the mechanism of pulmonary vasoconstriction, which functions to improve the oxygen saturation of the systematic arterial blood and the increased work load of the heart, could have reached a critical level. A continuing genetic and nutritional improvement in growth rate therefore may result in an increased incidence of HFS and ascites. Modern selection programs deal with a decreased feed conversion ratio (FCR). A better FCR can be obtained by reducing fat deposition in favor of increased protein accretion and by reducing energy requirements for maintenance. When combined with a considerable accumulation of water, protein accretion saves more feed energy than fat accretion does. Solun et al. (1972) showed that a lowered thyroid hormone production in farm animals, which is related to a reduced intensity of cell oxidation, and a diminished oxygen requirement, resulted in a low FCR. Wethli and Wessels (1973) confirmed mese relationships, and reported a tendency toward a low thyroid activity in chickens exhibiting a low FCR. Oxygen consumption is important with respect to HFS and ascites. Therefore, the results of investigations of Stewart et al. (1980) and Stewart and Muir (1982) with different populations of chickens selected for
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reduced pulmonary vascular bed, the heart has to respond by a more vigorous contraction to overcome the higher flow resistance. The inverse proportionality between flow resistance and the fourth power of the flow diameter accentuates the effect of pulmonary vasoconstriction, reducing directly the flow passage diameter, on the increased workload of the heart. Studies of Rosse and Waldmann (1966) showed that anoxia in birds stimulated red blood cell production, resulting in higher hematocrit values. Fahraeus and Lindqvist (1931), and Levy and Share (1953) found a direct relationship between hematocrit values and blood viscosity, which in turn is directly proportional to the flow resistance. A severe pulmonary vasoconstriction combined with increased hematocrit values in hypoxic chickens was found by Cueva et al. (1974) and Sillau et al. (1980). Heart insufficiency and heart failure succeeded pulmonary arterial hypertension and right ventricular hypertrophy in birds that died at high altitudes. Symptoms included a severe thickening of the atrioventricular valve and a general passive congestion in heart, lungs, and liver, accompanying ascites. Heart insufficiency and decreased cardiac output has further consequences. Levy (1979) demonstrated that a stepwise decrease in the output of the right ventricle resulted in a substantial rise of the venous pressure, including the portal vein and hepatic veins, which collect the interstitial fluid from the abdominal cavity. The incidence of edema and ascites in hypoxic fowl can be explained as follows. The transfer of fluid across the thin capillary walls in lung and liver is enhanced by higher resistance and pressure in the arterioles. The reabsorption of the interstitial fluid by the post capillary venules and the drainage capacity of the lympathic vessels can be severely blocked by a heightened venous pressure as a result of heart insufficiency. Such a disturbance in the delicate balance of fluids entering and exiting across the capillary walls will finally result in edema in lungs, hydropericardium, and ascites. Air sacs located in the abdominal cavity are of great importance in regulating the air flow rate entering and leaving the avian lung (Akester, 1978). By inhibiting the action of these air sacs ascites could further intensify hypoxic conditions leading to death. The
ASCITES IN BROILERS
MATERIALS AND METHODS
Chickens Chickens of two genetic groups were used: 1) a pure broiler sire population (SS),3 primarily selected for a favorable FCR combined with a high BW gain; and 2) a commercially available broiler cross (BC)3 in which SS was one of the grandparental populations.
received a standard broiler diet containing 13.4 MJ 4 ME and 215 g CP per kilogram. All chicks were spray vaccinated against Newcastle disease with the La Sota strain at 6 days of age. Experimental Period The experiment lasted from 1 through 5 wk of age. At 1 wk of age, birds from one T a treatment and stock (a flock) separately were divided into six weight classes (52 birds per class). Twentysix groups of 12 birds were formed from each flock by randomly taking 2 birds from each weight class making one group. From each flock, 2 of the 26 groups were killed by carbon dioxide inhalation and prepared for chemical analysis; these two groups served as reference groups in the energy balance measurements. The remaining 96 groups of 12 birds were placed in 96 battery cages (1 x .6 m) on raised wire floors arranged in four climatic rooms, three tiers, and eight cages. Temperature Regimens and Environment Starting at 1 wk of age, two experimental T a were used: a cold T a distinctly below the zone of thermoneutrality of these chicks during the experimental period (T a low) and a normal rearing T a for that period (T a high). The birds raised at a pretreatment regimen of 33 to 30 C were exposed to a regimen of 30 to 22 C (T a high) and those raised at 30 to 25 C were exposed to a regimen of 25 to 15 C (Ta low). During the period from 1 to 5 wk of age, the ambient temperatures were gradually reduced once a day. Relative humidity was kept constant at 60% for both T a regimens. Continuous light was given during the first 3 days in the batteries. After this time, a light regimen of 1 h light and 2 h of darkness was applied. Diets
The dietary experimental factors applied were energy and fat content. Two AME levels The two stocks were raised at two ambient (low and high) and two fat levels (low and high) temperature (Ta) regimens from 0 to 1 wk of age. were used, making four different diets. The The T a was gradually reduced, once a day, from diets, fed in mash form, were composed of 30 to 25 C and from 33 to 30 C, respectively, for normally available feed ingredients such as each regimen. During this period, all chicks maize, maize starch, maize gluten meal, maize gluten feed, wheat middlings, sugar, soybean meal, full fat soybeans, soybean oil, fish meal, sunflower meal, synthetic lysine and methio^uribrid BV, 5831 JN Boxmeer, The Netherlands. 4 nine, limestone, and commercial mineral and 1 MJ = 239 kcal.
Preliminary Period
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high and low O2 consumption supplied most interesting facts. Selection for low oxygen consumption resulted in a significantly better FOR and in a faster-growing and leaner bird. From these results the hypothesis postulated in this study was that a genetic improvement in FCR, in growth rate, and in protein to fat ratio, at least in some populations, might be correlated witii a reduced ability to consume oxygen. Environmental factors such as a low ambient temperature can stimulate the metabolism and increase the oxygen requirement. In these circumstances such birds will approach their long term metabolic limit (Scheele and Frankenhuis, 1989). This could initiate pulmonary hypertension and polycythemia, producing the same cardiac events and edema as occurs under conditions of high altitude. The objective of the present research was to study effects of ambient temperature, energy density of diets, and dietary fat content as factors used to stimulate metabolism in male broilers of two genetically related populations with divergent growth rates and FCR. Dissimilar responses of these populations to the stimulating factors could reflect genotype by environment interactions, revealing metabolic disorders related to HFS and ascites. The present study provides values for performance, energy metabolism, oxygen consumption, and hematocrit values at different ages during an experiment of 4 wk duration.
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SCHEELE ET AL. TABLE 1. Nutrient composition, heat of combustion, AME, AMEn, fat digestibility, and fat energy in AME determined in the experimental diets High AME
Low AME
Measurement
Low fat (Diet 1)
High fat (Diet 2)
Low fat (Diet 3)
High fat (Diet 4)
Protein (N x 6.25), g/kg DM Fat, g/kg DM Crude fiber, g/kg DM Heat of combustion, M^/kg DM AME, MJ/kg DM AME,,, Ml/kg DM Fat digestibility, % Fat energy in AME, %
266 64 19 19.39 15.84 15.03 91.6 14.4
264 169 34 21.47 16.15 15.31 91.8 37.4
246 51 32 18.93 14.39 13.67 90.3 12.5
238 139 53 20.68 14.42 13.69 90.8 34.1
'1 MJ = .239 Meal.
Measurements Feed intake and BW per cage were measured weekly. Deaths were recorded daily and all dead birds were necropsied. At 2, 3, 4, and 5 wk of age, blood samples were collected by venipuncture from one bird per cage. These birds were chosen randomly with the exception that no bird was sampled twice. Hematocrit (Ht) values were measured after centrifugation of the blood as a volume percentage. The AME, AMEn, and digestibility of the fat of the four diets were measured during the 4th wk of age for all cages in the middle tiers of the four climate rooms, according to Scheele and Jansen (1972). The energy retention (RE), protein deposition (RP), and fat deposition (RF) from 1 to 5 wk was measured according to the
comparative slaughter method (Scheele and Jansen, 1972). At 5 wk of age, the body composition was determined in a pooled sample of five randomly chosen chickens from each cage and compared with that of the birds corresponding in stock and T a treatment killed at 1 wk of age. The AME consumption of these five birds per cage was calculated by multiplying the mean FCR per kilogram of BW per cage by the AME value of the diet and by the total BW of the five birds taken for carcass analyses. The mean daily heat production (Hp) per chicken per cage from 1 to 5 wk of age was calculated by subtracting the mean daily RE from the mean daily AME intake (MEj). Verstegen et al. (1987) presented a simple equation to calculate Hp sufficiently accurate from either carbon dioxide production or oxygen consumption (OXc), using a fixed value for the respiratory quotient (RQ). In this experiment OXc (L) was calculated from Hp (kJ) according to the following simplified equation using a RQ of .90: Hp = 20.70 OX^ or OXc = .048 Hp; where MEj, RE, and OXg were calculated per day per unit of metabolic body weight (W*). W* = (Mean BW in kilograms per cage at 5 wk + mean BW in kilograms per cage at 1 wk)/2-75. The main effects and two factor interactions will be discussed. Least significant differences based on two sided tests ( a = .05) were calculated according to Satterthwaite (1946). Statistical Analysis An experiment with a 2 x 2 x 2 x 2 factorial split-plot arrangement of treatments was performed to investigate the effects of ambient temperature regimen (low or high), stock (BC,
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vitamin mixtures. For the digestibility experiments . 1 % Cr2C>3 was added as a marker. Low fat diets contained mainly carbohydrates with low crude fiber contents. In high fat diets, these carbohydrates were exchanged isoenergetically by soybean oil together with low energy feedstuffs containing considerable amounts of crude fiber. Differences in dietary crude fiber contents were also created using two AME levels. In this way crude fiber contents were not automatically connected with fat contents. Effects of crude fiber therefore could be separated from effects of dietary fat. The calculated ratios of CP, lysine, and methionine plus cystine to megajoules of A M E Q in 1 kg feed were 17, .97, and .73, respectively, for all diets. The determined chemical and digestible nutrient composition of the diets is given in Table 1.
ASCITES IN BROILERS
RESULTS
Dietary Parameters Table 1 shows the results of the chemical and physical analyses of the diets and the determined values for the AME—the AME,, as used in feeding tables. Also given are the digestibility coefficients of dietary fat and the percentage of fat energy in the AME. Because the experimental factors of broiler stock and ambient temperature did not show any significant effect (P>.05) on measured AME or fat digestibilities, only mean values are given for each diet. Performance Data and Hematocrits In Table 2, the probability values of significance tests of effects of T a , stock, dietary energy, and dietary fat, and their interactions on performance data and hematocrits at different ages are given. Means of performance data as affected by main factors are shown in Table 3. Body weight gain was clearly effected by stock, dietary AME (P<.001), and fat (P<.05) content
at all ages. The SS birds, the high AME level, and the low fat content in the diets had a positive effect on BW gain. Feed intake was significantly affected by T a (P<.05) and by AME and fat (P<.001) at all ages (Tables 2 and 3). A low T a , a low AME diet containing large amounts of crude fiber, and a low fat diet containing little crude crude fiber increased feed intake. No main effect of stock on feed intake was found. This resulted in a strong effect of stock on FCR. The SS birds showed a better FCR than the BC birds during the entire experimental period. Generally, a low feed intake was accompanied by a low FCR (Tables 2 and 3). Consequently, a high AME and high fat content had a positive effect (P<.001) on FCR. The positive effect of a high T a on FCR increased with age. Significant effects (P<.05) of T a on Ht values were found at 2 and 5 wk of age (Tables 2 and 4). Stock had an increasing effect on Ht values with age, with differences being significant at 3 wk (P<.05) and highly significant at 4 and 5 wk (P<001). Effects of dietary energy and fat on Ht values were only significant (P<.05) at the end of the experimental period at 4 and 5 wk of age, respectively. At different ages, distinctly higher Ht values were found at a low T a and in SS birds (Table 4). Interactions Between Stocks and Ambient Temperatures Some important and highly significant interactions between stocks and T a on performance traits were found (Tables 2 and 5). The effect of T a on BW gain at 3, 4, and 5 wk of age was highly dependent on stock. The low T a stimulated BW gain of the BC broilers but affected BW gain negatively in the SS stock. Also, the effect of T a on feed intake was significantly (P<001) dependent on stock (Tables 2 and 5). As the low T a was clearly below the zone of mermoneutrality for these chickens (Scheele et al., 1987), the BC broilers demonstrated a normal reaction at the low T a by a distinctly increased feed intake compared with intake at the high T a . However, the reaction of the SS broilers on the low T a was strikingly different. Compared witii die BC, die SS broilers only slightly increased feed intake in the cold environment, indicating tiiat these birds were not able to consume sufficiently more energy to produce die extra heat demanded by the cold environment. Consequently, die BW gain of me
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SS), dietary fat (low or high), and dietary energy (low or high). Each temperature regimen was replicated twice. The regimens were randomly assigned to four climate rooms. Within each climate room the eight factorial combinations of stock, dietary fat, and dietary energy were randomly assigned to the eight cages within each tier. Performance data, hematocrits, and energy parameters were analyzed by ANOVA using the model: Yjjkinu,=|J.+T} + ejj + e ljk + Sj + F m + EQ + interactions + e^onm; where Y = observed value of the parameter to be analyzed; \i is the common mean; T, is the effect of the i"1 temperature regimen; Si is the effect of the 1th strain; F m is the effect of the nr* dietary fat level; F^ is the effect of the ifi dietary energy level; interactions stand for all interactions between 2, 3, and 4 factors; eij, ejjfc, and qjkinu, are random errors for climate rooms, tiers within rooms, and cages within tiers, respectively. These random errors were assumed to be independently and normally distributed with variances of a 2 room, a 2 tier, and a 2 cage, respectively. The effect of temperature regimen was tested by using the mean square error for rooms, based on 2 df. The remaining effects and interactions were tested by using die mean square error for cages within tiers based on 70 df.
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TABLE 2. Probability values of significance test of main effects and interactions among experimental factors1 on performance traits and hematocrit values in broilers at different ages Experimental period 1 1 1 1
to to to to
2 3 4 5
wk wk wk wk
1 1 1 1
to to to to
2 3 4 5
wk wk wk wk
1 1 1 1
to to to to
2 3 4 5
wk wk wk wk
2 3 4 5
wk wk wk wk
Ta
*
T a X E Ta X F S x E • Body weight gain (grams per bird per d.inrt y)
Stock (S)
AME, (E)
Fat, (F)
T,xS
*** ***
*** *** *** ***
* * * *
** *** ***
**+
***
S x F
E x F
** **
** * *
Feed intake (grams per bird per day)
* ** ***
** *** *** ***
* *
* *
* **
Feed conversion ratio (g:g)
*** *** *** ***
*** *** *** *+*
** *** *** ***
* *** ***
*
*
**
*** *** *
** ** ***
* *
*
. . .
1 T a =two ambient temperatures; Stock=two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broiler cross (BC) in which SS was one of the grandparental lines; AME, and dietary fat (fat) both at low levels. *P<05. **P<.01. ***P<.001.
TABLE 3. Mean values for body weight gain, feed intake, and feed conversion ratio of broilers at different ages as affected by experimented factors1
Low
period
High
BC
to to to to
2 3 4 5
wk wk wk wk
234 611 1,062 1,520
229 611 1,079 1,524
225 594 1,039 1,479
1 1 1 1
to to to to
2 3 4 5
wk wk wk wk
301 857 1,621 2,518
286 814 1,543 2,393
293 832 1,576 2,449
1 1 1 1
to to to to
2 3 4 5
wk wk wk wk
1.25 1.33 1.43 1.57
Low
SS
1 1 1 1
1.29 1.40 1.53 1.66
AME
Stock
T *a
1.30 1.40 1.52 1.66
- Body weight gain (g) 226 238 628 601 1,102 1,054 1,565 1,494 Feed intfllr** t**\ 294 300 838 857 1,624 1,589 2,461 2,521 1.24 1.34 1.44 1.57
1.33 1.43 1.54 1.69
Fat
High
Low
High
237 620 1,088 1,550
238 628 1,093 1,545
225 593 1,048 1,499
287 813 1,541 2,389
307 875 1,642 2,526
280 796 1,522 2,384
1.21 1.31 1.42 1.54
1.30 1.39 1.50 1.64
1.24 1.34 1.46 1.59
! T a =two ambient temperatures; Stock=two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broilerCTOSS(BC) in which SS was one of the grandparental lines; AME, and dietary fat (fat) both at low levels.
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*** *** *** ***
* * * *
ASCITES IN BROILERS
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TABLE 4. Mean hematocrit values of broilers at different ages as affected by experimental factorr Stock
Fat
AME
Age
Low
High
SS
BC
2 3 4 5
30.4 31.1 32.9 32.7
28.5 29.4 31.1 29.4
29.6 31.1 33.7 32.3
29.3 29.4 30.3 29.7
Low
High
Low
High
29.7 29.9 31.0 30.5
29.3 30.6 32.9 31.5
29.5 30.3 32.0 30.3
29.5 30.2 32.0 31.7
CWl wk wk wk wk
*Ta=two ambient temperatures; Stock=two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broiler cross (BC) in which SS was one of the grandparental lines; and AME, and dietary fat (fat) both at low levels.
Interactions Between Dietary Fat Content and Other Experimental Factors Effects of dietary fat on the performance of the broilers were significantly dependent on T a and stock, as is shown in Tables 2 and 6. It is important to note that interactions between dietary energy and T a or stock differed among the cases. This indicated that the effects of dietary fat in the interactions were mainly independent of effects of dietary crude fiber. In
TABLE 5. The significant (P<.05) interactions between stockr and ambient temperature on performance data and hematocrit values of broilers at different ages Stock x Ta SS
BC
Experimlental period
Low Ta
High Ta
Low T a
High T a
LSDx2
LSD 2 3
1 to 3 wk 1 to 4 wk 1 to 5 wk
600 1,044 1,498
589 1,034 1,460
622 1,080 1,542
633 1,124 1,587
12 22 35
18 17 38
304 867 1,645 2,561
282 798 1,507 2,337
7 16 32 57
14 32 34 51
1 1 1 1
to to to to
2 3 4 5
wk wk wk wk
1 1 1 1
to to to to
2 3 4 5
wk wk wk wk
4 wk
1.33 1.45 1.58 1.71 30.2
1.28 1.36 1.46 1.60 30.3
298 290 846 830 1,598 1,579 2,474 2,448 - Feed conversion ratio (g:g) — 1.25 1.36 1.48 1.61 35.6
1.23 1.31 1.41 1.54 31.8
.01 .01 .01 .02 2.1
.02 .04 .02 .01 3.1
'T, = two ambient temperatures; Stock = two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broiler cross (BQ in which SS was one of the grandparental lines; AME and dietary fat (fat) both at low levels. LSDj = least significant difference comparing two means within the same Ta regimen. = least significant difference comparing two means with different Ta regimens.
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SS birds, in contrast to the BC birds, was negatively affected by the low T a . The relatively low level of feed intake of SS birds at a low T a is also reflected in the interaction of stock and T a on FCR (Tables 2 and 5). Due to the rather constant feed intake, FCR of the SS birds increased only slightly at a decreased T a , but this was clearly different from the BC birds. At 4 wk ofage, the effect of T a on Ht values was strongly dependent on stock. The SS birds probably had a shortage of oxygen consumption at a low T a .
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SCHEELE ET AL. TABLE 6. The significant (P<.05) interactions of dietary fat1 with ambient temperature, with stock, and with dietary AME, on performance data of broilers at different ages Fat x T a High fat
Low fat
Experinilental period
Low T a
High T a
Low T a
High T a
LSDj 2
LSD 2 3
1 to 3 wk 1 to 4 wk 1 to 5 wk
635 1,094 1,558
621 1,092 1,533
587 1,030 1,483
600 1,066 1,515
12 22 35
18 17 38
1 to 2 wk 1 to 3 wk
317 902
297 847
285 811
275 780
7 16
14 32
1.41 1.54 1.67
1.39 1.52 1.65
1.37 1.47 1.61
1.30 1.40 1.54
.01 .01 .02
.04 .02 .01
Fat x stock Low fat BC
High fat BC
SS
SS
1 to 2 wk 1 to 3 wk
228 606
248 651
222 583
228 604
6 12
1 to 2 wk 1 to 3 wk
304 865
311 884
282 800
278 792
6 16
1 to 2 wk
1.34
1.27
1.26
1.22
.01
Fat x AME High fat
Low fat Low AME 1 to 2 wk 1 to 3 wk 1 to 4 wk
1.34 1.44 1.56
High AME
Low AME
1.25 1.34 1.45
1.32 1.41 1.52
High AME 1.17 1.28 1.39
.01 .01 .01
T",=two ambient temperatures; Stock=two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broiler cross (BQ in which SS was one of the grandparental lines; AME and dietary fat (fat) both at low levels. LSDx = least significant difference comparing two means within the same temperature regimen. \SI>2 = least significant difference comparing two means with different T a regimens.
periods 1 to 3,1 to 4, and 1 to 5 wk of age the fat by T a interaction was clearly affecting BW gain, In these periods the combination of low T a and high fat had a marked detrimental influence on BW gain. With the low fat diets, a low T a had a fi o*;m,Tw; ~te * nnr • W stimulating effect on BW gam. By lowering T a , the increase in feed intake was less with the high than with the low fat diet (Tables 2 and 6). The birds seemed to be inhibited from consuming more feed if the diets
contained a high quantity of fat. These results indicated that chickens had problems metabolizm g i^gg quantities of dietary fat. The notably ^ ^ F C R a t a Ugh fat content, even when „„, . . 7 « . j ., w gain was reduced, was affected greatly by , . , . , . , , , . , _ . „ 7 , , me "**>tod feed intake. Especially in the last weeks, the effect of an increased fat content on FCR was much greater at a high T a than at a low Ta.
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1 to 3 wk 1 to 4 wk 1 to 5 wk
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ASCITES IN BROILERS
Mortality Rates The mortality rate was 4.5%. Heart failure syndrome and ascites were the most important causes of death. Deaths related to experimental factors are shown in Table 7. Table 7 also lists numbers of dead birds in which no pathogenic abnormalities were found other than HFS or
ascites. From 36 birds with severe symptoms of HFS and ascites, 24 birds belonged to the SS stock kept at a low temperature. Energy Metabolism In Table 8, the probability values of significance tests of effects of the experimental factors on energy metabolism parameters over the period from 1 to 5 wk of age are presented. The means of energy metabolism data for the levels of the experimental factors are given in Table 9. The ME; per unit of metabolic BW was strongly affected by all factors. With the exception of T a , the experimental factors appeared to have marked effects on RE per unit of metabohc B W. The effects of the dietary factors were highly significant (P<.001). The RE per unit of metabolic BW was higher in the BC than in the SS birds. When energy retention is expressed in kilojoules per day per bird, the RE, as well as deposited protein and fat in grams per day per bird, were highest in the SS birds. The ratio of energy deposition to BW gain was different for both stocks. High energy and low fat diets clearly favored RE per unit of metabolic weight. Oxygen consumption was enhanced by a low T a , which was directly related to a higher heat production. High energy and low fat diets showed the highest rate of deposition of protein and fat, which correlates with the higher ME, values with these diets (Tables 8 and 9). Protein deposition, and thus also accumulation of water, was significantly (P<.001) higher in SS birds than in BC birds. Weight gained through water retention is reflected in the better FCR of SS stock. All experimental factors had important effects on the energetic efficiency of the diets for
TABLE 7. Total mortality during the experimental period, and mortality caused by heart failure syndrome (HFS) and ascites (number of birds) Dietary factors Stock
Ta Mortality
Low
High
BC
SS
Low AME
High AME
Low fat
High fat
Total HFS Ascites
37 10 18
15 6 2
14 5 2
38 11 18
30 12 12
22 4 8
28 10 11
24 6 9
T a =two ambient temperatures; Stock=two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broiler cross (BC) in which SS was one of the grandparental lines; AME, and dietary fat (fat) both at low levels.
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At 2 and 3 wk of age, a significant (P<.01) interaction between fat and stock affecting BW gain was revealed (Tables 2 and 6). In these periods, the difference between stocks was markedly more pronounced at the low than the high fat level. The SS broilers obviously could not fully utilize tiieir higher capacity for growth when high fat diets were fed. An interesting difference was found between stocks at 1 to 2 wk and 1 to 3 wk of age in their feed intake response to differences in dietary fat content (Tables 2 and 6). Only with low fat diets did the SS consume significantly (P<.05) more feed than the BC. This indicates that the SS chickens were more sensitive to a high fat content in diets than the BC broilers. Li regard to FCR, the differences between stocks during the first experimental week were significantly (P<.05) greater at a low dietary fat level compared with a high fat content (Tables 2 and 6). The high productive capacity of the SS was reduced when environmental circumstances were less favorable. Another interaction affecting FCR significantly (P<001) was dietary AME by dietary fat level. The beneficial effect of a high fat content on FCR as a result of a lowered feed intake was most pronounced in high energy diets, hi fact, the high fat content prevented an overconsumption of dietary energy, which can happen when highly concentrated diets are fed.
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TABLE 8. Probability values of significance tests of effects of experimental factors^ on AME intake (MEj), energy retention (RE), and oxygen consumption (OXe) all calculated per metabolic weight (W*), on deposited fat (RF) and protein (RP), and on efficiency of MEj for body weight gain (BWGIMEj) in broilers from 1 to S wk of age Variable2 MEj/W* RE/W* OXc/W* RF RP BWG/MEj
Ta
Stock (S) AME, (E) Fat, (F)
*** ***
*** ***
*** ***
*** * ***
***
T,xS
I,xE
T,xF
S x E
S x F
E x F
***
BW gain expressed as BW gain:MEi (Tables 8 and 9). The highest efficiency was obtained at a high T a , from SS birds, with low AME and high fat content in diets. In all these cases, the high efficiencies corresponded to relatively low values for ME}. Interactions Between Factors in Respect to Energy Metabolism The T a factor was involved in all important interactions affecting energy metabolism variables. The highly significant (P<001) effect of
the interaction of T a by stock on MEj per metabolic weight pointed distinctly to the relative low MEj at a low T a of the SS birds compared with the BC birds. At a high T a , SS birds did not consume less energy than BC. Also the effect of the T a by stock interaction on OXc revealed striking differences in metabolism (Table 10). At a low T a , a higher OXc was required in both stocks to meet the increased demand for heat production. But at the same metabolic BW, the OXg at a low T a was significantly (P<.01) lower for the SS than for the BC. At a low T a the SS stock was not able to
TABLE 9. Mean values of AME intake (MEj), energy retention (RE), and oxygen consumption (OXe) all calculated per metabolic weight (W*), of deposited fat (RF) and protein (RP), and of efficiency of MEj for body weight gain (BWG/MEi) in broilers from J to 5 wk of age as affected by experimental factors'
Variable2
Low
MEj/W* RE/W* OXc/W* RF RP BWG/MEi
1,342 565 37.7 7.1 10.1 46.6
Ta High 1,273 590 33.2 7.8 9.9 49.2
AME
Stock
Fat
BC
SS
Low
High
Low
High
1,320 585 35.7 7.6 9.8 46.7
1,295 571 35.1 7.3 10.2 49.1
137 557 35.4 6.9 9.9 48.4
1,328 598 35.4 8.0 10.1 47.4
1,327 598 35.0 8.0 10.1 47.5
1,288 557 35.8 6.9 9.9 48.3
T a = two ambient temperatures; Stock=two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broiler cross (BC) in which SS was one of the grandparental lines; AME, and dietary fat (fat) both at low levels. 2 MEi and RE in kilojoules per day (lkJ = .239 kcal); OX,, in liters per day, W* = mean body weight in kilograms to the power .75, RF and RP in grams per day, BWG/MEj in grams per megajoule.
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4",=two ambient temperatures; Stock=two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broiler cross (BC) in which SS was one of the grandparental lines; AME, and dietary fat (fat) both at low levels. 2 ME; and RE in kilojoules per day (lkJ = .239 kcal); OXe in liters per day, W* = mean body weight in kilograms to the power .75; RF and RP in grams per day; BWG/ME; in grams per megajoule. *P<05. **P<01. ***P<.001.
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energetic efficiency BW gain:MEj also was affected by the interaction of T a by dietary fat (P<.001). A beneficial effect of a high dietary fat content caused by a reduced MEj on BW gain: MEj was found only at a high T a . The high dietary fat level reduced ME, noticably less at a low T a . Furthermore, a high fat level resulted in a higher heat expenditure at a low T a . Consequently, at a low T a , no positive effect of a high fat level on BW gain:MEj was found. DISCUSSION
Stimulating the metabolism of two different broiler populations by T a and by dietary factors resulted in dissimilar responses revealing metabolic dysfunctions. Interactions between stock and ambient temperature or dietary fat demonstrated clearly that the SS birds, which were selected primarily for a low FCR, were more sensitive to stimulating factors man the commercial BC birds. The SS birds had difficulty adapting to changes in their environment. Consequently, differences
TABLE 10. The significant (P<.05) interactions of TJ with stock, with dietary AME and with dietary fat on AME intake (ME;), and oxygen consumption (OXc) both calculated per metabolic weight (W*), and on efficiency of MEj for body weight gain (BWG/MEj) in broilers from 1 to 5 wk of age T a x stock High T a
Low T a Variable2
BC
SS
BC
SS
LSD! 3
LSD 2 4
ME/W* OX^/W* BWG/MEi
1,369 38.6 45.1
1,314 36.7 48.1
1,271 32.7 48.4
1,276 33.6 50.1
15 1.3 .6
13 1.3 .5
.6
.5
15 1.7 .6
13 1.7 .5
T a X AME High T a
Low T a Low AME BWG/MEi
46.8
High AME 46.4
Low AME 49.9
High AME 48.5
T8, x fat High T a
Low T a MEj/W*
oxyw* BWG/MEi
Low fat
High fat
Low fat
High fat
1,355 36.8 46.6
1,329 38.6 46.6
1,299 33.2 48.4
1,248 33.0 50.1
1 T a = Two ambient temperatures; stock = two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a comeicially available broiler cross (BC) in which SS was one of the grandparent lines; AME, and dietary fat (fat) both at low levels. 2 MEi in kUojoules per day (lkj = .239 kcal); OX,, in liters per day; BWG/ME; in grams per MJ; W* = mean body weight in kilograms to the power .75. \S0\ = Least significant difference comparing two means within the same T a regimen. 4 LSD 2 = Least significant difference comparing two means with different T a regimens.
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consume enough oxygen to maintain the relatively high metabolic rate compared with the BC, as was demonstrated at a high T a . Consonant with those findings was the effect of the T a by stock interaction on BW gain:MEj. Due to a low heat production rate at a low T a , the relatively high energetic efficiency of the SS for growth differed more from that of the BC at low T a than at high T a . The significant interaction (P<.01) between T a and AME for BW gain:MEi indicated that at a high T a the birds exhibited an overconsumption of dietary energy through high energy diets. The significant (P<.05) interaction between T a and fat in the effect on MEj per metabolic BW means that at a high T a the depressing effect of fat on MEj was more pronounced than at a low T a (Table 10). A significant (P<.05) interaction of T a by dietary fat was found in the effect on OXg. Despite a depressed MEj caused by a high dietary fat level, the heat expenditure at the low T a , and thus the oxygen consumption, were enhanced by that high fat level. As a result the
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Mortality was not high in the present experiment. However, two-thirds of the examined dead birds suffering from HFS or ascites belonged to the SS broilers kept at a low T a . At a low T a , SS birds demonstrated a lower OXg and higher hematocrits relative to the BC broilers. This is in agreement with findings reported by Sillau et al. (1980), Van Blerk (1985), and Van der Hel et al (1988), who related symptoms of heart failure and edema, including ascites and high hematocrits, to a lowered partial oxygen pressure. Notably, the SS birds fed high AME diets showed higher hematocrits in the 4th wk of age. As concentrated diets stimulate metabolism, this interaction between stock and dietary energy level illustrated that SS birds were near their long term metabolic limit. Effects of different dietary AME levels in this experiment were as expected. The high energy diet had a positive effect on BW gain and energy retention. The birds fed the low energy diets tried to compensate by consuming more feed, however, they were not able to eat the same amount of AME per day as birds fed the high AME diets. The latter deposited more fat but only slightly more protein. As a result of the lower MEj, a relatively high level of protein deposition, and a considerable accumulation of water, the birds fed the low AME diets exhibited the highest energetic efficiency for BW gain. In some cases the main effects of low energy diets and of high fat diets were similar. Low energy and high fat diets with relatively high crude fiber contents showed a reduced energy consumption resulting in a lower BW gain and in less deposition of fat. This indicates that a high crude fiber content might have contributed to the effects of these diets. The important differences among effects of low energy and high fat point to the important role of dietary fat per se in this experiment. First, the observed reductions in BW gain and feed intake caused by high fat diets were most pronounced in high energy diets. In high energy diets, crude fiber with maximum contents of 34 g/kg feed was of minor importance. Therefore, the effects of high fat diets indicated that both stocks exhibited problems in either digestion of fat or in lipid metabolism after intestinal absorption. Second, the highly significant interactions between dietary fat and whether stock or ambient temperature illuminated the specific
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in BW gain, feed intake, FOR, Ht values, MEj, OXg, and weight gain:MEj between stocks were markedly dependent on environmental temperature and also on dietary fat level. The relative retardation of BW gain and feed intake and the relatively high Ht values of SS broilers compared with BC birds when metabolism was forced were similar to effects found under hypoxic conditions (Sillau et al, 1980; Van der Hel et al, 1988; Julian et al, 1989). The high Ht values in SS birds at a low T a corresponded very well with the observed low level of OXc per metabolic BW compared with the BC broilers. This result is similar to those reported from experiments under hypoxic conditions, and indicates the inability of the SS birds to adapt metabolically to changes in the environment. The SS chicks hardly increased their feed intake or ME, at the low T a compared with the high T a . As protein gain was not affected by T a , the difference in FCR and in BW gain:MEj between the two stocks was most pronounced at a low T a . Clearly, a high energetic efficiency for growth can have a negative significance when this is connected to a situation of stress. The results indicated that the SS birds grown at the low T a were forced to save energy at the cost of heat production and fat deposition, perhaps because they did not have the capacity for a high rate of combustion of chemical energy. The low heat production rate and low OXg at low temperatures signals inadequate metabolic action. Under unfavorable environmental conditions, this can lead to imbalances resulting in pulmonary hypertension, cardiac hypertrophy, heart failure, hypoxaemia, and finally, to edema resulting in ascites. The results indicated a relationship between a low rate of OX,, and FCR, particularly at a low T a . This confirms the results of Stewart and Muir (1982). Selection for a low FCR may be accompanied by a decreased respiratory exchange, which might be related to an inability to consume sufficient oxygen. This concept is sustained by observations of Huchzermeyer et al (1988), who reported that commercial broiler strains differ in their susceptibility for pulmonary hypertension syndrome. It was concluded that an effective abatement of diseases like ascites could be encouraged by examining the development of relevant metabolic parameters during selection of the domestic fowl on exterior traits like growth rate and FCR.
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and OXg were significantly higher with high fat diets compared wim low fat diets. Obviously, digestion of fat was more than sufficient to deliver the fuel needed for protein synthesis and for combustion to heat. The clearly depressed deposition of body fat by chickens consuming high fat diets reveals problems in the synthesis and retention of body fat. Studies of Leveille et al. (1975), Hillard et al. (1980) and Tanaka et al. (1983) elucidated how a high dietary fat content exerted a depressing effect on hepatic lipid synthesis either by the dietary fat level per se or by the simultaneously decreased carbohydrate level in the diet. Carew and Hill (1964) found that, in spite of such a reduced fat synmesis, the deposition of fat in chicken tissues directly from ingested fat was clearly enhanced as the dietary level of com oil was increased up to 22.5%. Carew et al. (1963) also found beneficial effects of high levels of dietary soybean oil, independent of density of diets, on BW gain of chickens. This is in marked contrast with the results of the present study using low and high levels of soybean oil. Possibly, SS and BC birds have limited abilities to synthesize or to deposit fat, because selection for FCR is correlated wim lower body fat values. During selection for characteristics such as FCR, which will have an impact on metabolism, attention may have to be given to changes in metabolic parameters governing heat production and oxygen consumption (maintenance) and protein and fat synthesis. Only then can a development of undesired pathways in metabolic processes be avoided. The results of the present experiment suggest that in the SS birds, a fast protein gain was achieved together with a reduced ability of converting chemical energy to heat and of depositing fat in tissues directly from dietary fat. Such metabolic reductions point to less flexibility in adaptation of metabolism to a changing environment. Finally, the additive sum of these kinds of stressing factors can account for development of metabolic disorders such as heart failure syndrome and ascites. REFERENCES Akester, A. R., 1978. Microcirculation in birds. Pages 687-735 in: Microcirculation. Vol. 2, Chapter 18. G. Kaley and B. M. Altura, ed. University Park Press, Baltimore, MD.
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role of fat as a source of dietary energy in poultry metabolism. It appeared that die SS chickens were less tolerant of the high fat diets than the BC chicks. At the low fat level, the SS birds exhibited die greater positive difference in BW gain, feed intake, and FCR compared with BC broilers. In these circumstances, the SS birds showed that, relative to the BC birds, they were able to consume large quantities of feed including low energy diets. A striking result was obtained by comparing the SS birds with the BC birds at 3 wk of age when fed diets with a high fat content. The feed intake of tihese SS birds was even less than that of the BC. The negative impact of high dietary fat levels on SS chickens reflected the greater sensitivity of this stock for stressing factors in metabolism. High fat diets primarily resulted in less deposition of fat, protein deposition was only slightly affected, and the overall result was a better FCR. This may indicate that in some cases a favorable FCR can be associated with an inhibition of metabolism, which could cause metabolic disorders. Rand et al. (1958), Renner (1964), and Brambalia and Hill (1966) reported mat the chicken is tolerant of low carbohydrate and high fat diets up to 30% dietary fat. Comparing their results obtained more man 20 yr ago with the present experiment with modern broiler stocks indicates that selection can create birds with less tolerance to high fat diets. At 5 wk of age, increased dietary fat resulted in significantly higher Ht values. Combustion of fat energy to heat requires more oxygen man combustion of carbohydrate energy. Differences in dietary fat interacted importantly with differences in T a . Especially at the low T a the depressing effect of fat on feed intake and ME} and on BW gain was clearly pronounced. When a higher intake was needed because of a higher thermal demand of the environment, the birds fed the high fat diets were not able to consume enough feed to meet their energy requirements for growth. Problems with digesting large quantities of fat could explain the low energy intake within high fat diets. The observed high digestion coefficients of fat (Table 1), in the present experiment, however, point to other causes. At a low T a , even when high fat diets lowered ME;, virtually no effect on protein deposition could be found. Furthermore, heat production
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SCHEELE ET AL. 247-255. Olander, H. J., R. R. Burton, and H. E. Adler, 1967. The pathophysiology of chronic hypoxia in chickens. Avian Dis. 11:609-620. Rand, N. T., H. M. Scott, and F. A. Kumerov, 1958. Dietary fat in the nutrition of the growing chick. Poultry Sci. 37:1075-1085. Rentier, R., 1964. Factors affecting the utilization of carbohydrate-free diets by the chick. I. Level of protein. J. Nutr. 84:322-326. Rosse, W. F., and T. A. Waldmann, 1966. Factors controlling erythropoiesis in birds. Blood 27: 654-661. Rostorfer, H. H., and R. H. Rigdon, 1947. The relation of blood oxygen transport to resistance to anoxia in chicks and ducklings. Biol. Bull. 92:23-30. Satterthwaite, F. E., 1946. An approximate distribution of estimates of variance components. Biometrics Bull. 2:110-114. Scheele, C. W., and M. T. Frankenhuis, 1989. Stimulation of the metabolic rate in broilers and the occurrence of metabolic disorders. Pages 251-255 in: Energy Metabolism of Farm Animals. European Association of Animal Production Publication Number 43. Y. van der Honing and W. H. Close, ed. Pudoc, Wageningen, The Netherlands. Scheele, C. W., W. van der Hel, M.WA. Verstegen, and A. M Henken, 1987. Climatic environment and energy metabolism in broilers. Pages 217-261 in: Energy Metabolism of Farm Animals with Special Reference to Effects of Housing, Stress and Disease. M W A . Verstegen and A. M. Henken, ed. Martinus Nijhoff, Dordrecht, The Netherlands. Scheele, C. W., and B. P. Jansen, 1972. Standardization of nitrogen-balance experiments with rats. 2. Experimental procedure and techniques used in the evaluation of the experiments. Z. Tierphysiol. Tierernahr. Futtermittelkd. 28:24-28. Scheid, P., and J. P. Holle, 1978. Adjustment of the regional pulmonary circulation to the profile of oxygen pressure along the parahronchus in the duck. Pages 105-111 in: Respiratory Function in Birds, Adult and Embryonic. Johannes Piiper, ed. SpringerVerlag, Berlin, Germany. Schmidt-Nielsen, K., 1983. Animal Physiology: Adaptation and Environment Cambridge University Press, New York, NY. Sillau, A. H., S. Cueva, and P. Morales, 1980. Pulmonary arterial hypertension in male and female chickens at 3300 m. Pflugers Archiv. Eur. J. Physiol. 385: 269-275. Solun, A. S., L. M. Yakimenko, V. L. Mikhailov, L. N. Selivanova, and Z. A. Tkachek, 1972. Ispol'zovanie khlomokislogo ammoniya pri otkorme sel'skokhozyaistvennykh zhivotnykh. Khim. Sel'sk. Khoz. 10:925-931. Stewart, P. A., and W. M. Muir, 1982. The effect of varying protein levels on carcass composition and nutrient utilization in two lines of chickens divergently selected for Oj consumption. Poultry Sci. 61: 1-11. Stewart, P. A., W. M. Muir, J. J. Begin, and T. H. Johnson, 1980. Feed efficiency and gain responses to protein levels in two lines of birds selected for oxygen consumption. Poultry Sci. 59:2692-2696. Sykes, A. H., 1960. A note on the determination of oxygen in the blood of the fowl. Poultry Sci. 39:16-18. Tanaka, K., S. Ohtani, and K. Shigeno, 1983. Effect of
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on May 30, 2015
Alexander, A. F., D. H. Will, R. F. Grover, and J. T. Reeves, 1960. Pulmonary hypertension and right ventricular hypertrophy in cattle at high altitude. Am. J. Vet. Res. 21:199-204. Atland, P. D., 1961. Altitude tolerance of chickens and pigeons. J. Appl. Physiol. 16(1):141-143. Brambila, S., and F. W. Hill, 1966. Comparison of neutral fat and free fatty acids in high lipid-low carbohydrate diets for the growing chicken. J. Nutr. 88:84-92. Burton, R. R., E. J. Besch, and A. H. Smith, 1968. Effect of chronic hypoxia on the pulmonary arterial blood pressure of the chicken. Am. J. Physiol. 214: 1438-1442. Carew, L. B., and F. W. Hill, 1964. Effect of corn oil on metabolic efficiency of energy utilization by chicks. J. Nutr. 83:293-299. Carew, L. B., M C. Nesheim, and F. W. Hill, 1963. The relationship of dietary energy level and density to the growth response of chicks to fats. Poultry Sci. 42: 710-718. Cueva, S., H. Sillau, A. Valenzuela, and H. Ploog, 1974. High altitude induced pulmonary hypertension and right heart failure in broiler chickens. Res. Vet. Sci. 16:370-374. Fahraeus, R., and T. Lindqvist, 1931. The viscosity of the blood in narrow capillary tubes. Am. J. Physiol. 96: 562-568. Grover, R. F., W. W. Wagner Jr., I. F. MacMurtry, and J. T. Reeves, 1983. Pulmonary circulation. Pages 103-106 in: Handbook of Physiology, Section 2: The Cardiovascular System-Peripheral Circulation and Organ Blood Flow. Vol. EI. Am. Physiol. Soc, Bethesda, MD. Hillard, B. L., P. Lundin, and S. D. Clarke, 1980. Essentiality of dietary carbohydrate for maintenance of liver lipogenesis in the chick. J. Nutr. 110: 1533-1542. Huchzermeyer, F. W., 1984. Waterbelly. Altitude disease. Poult. Bull. (June):279-281. Huchzermeyer, F. W., A.M.C. de Ruijck, and H. van Ark, 1988. Broiler pulmonary hypertension syndrome ID. Commercial broiler strains differ in their susceptibility. Onderstepoort J. Vet. Res. 55:5-9. Julian, R. J., 1987. The effect of increased sodium in the drinking water onrightventricular hypertrophy, right ventricular failure and ascites in broiler chickens. Avian Pathol. 16:61-71. Julian, R. J., G. W. Friars, H. French, and M. Quinton, 1987. The relationship of right ventricular hypertrophy, right ventricular failure and ascites to weight gain in broiler and roaster chickens. Avian Dis. 31: 130-135. Julian, R. J., I. McMillan, and M. Quinton, 1989. The effect of cold and dietary energy on right ventricular hypertrophy, right ventricular failure and ascites in meat-type chickens. Avian Pathol. 18:675-684. Leveille, G. A., D. R. Romsos, Y. Y. Yen, and E. K. O'Hara, 1975. Lipid biosynthesis in the chick. A consideration of site of synthesis, influence of diet and possible regulatory mechanisms. Poultry Sci. 54: 1075-1093. Levy, M. N., 1979. The cardiac and vascular factors that determine systematic blood flow. Circ. Res. 44: 739-746. Levy, M. N., and L. Share, 1953. The influence of erythrocyte concentration upon the pressure-flow relationships in the dog's hind limb. Circ. Res. 1:
ASCITES IN BROILERS increasing dietary energy on hepatic lipogenesis in growing chicks, n. Increasing energy by fat or protein supplementation. Poultry Sci. 62:452-458. Van Blerk, S., 1985. Changing disease picture for broilers. Poult. Int. (December): 19-24. Van der Hel, W., A. M. Henken, J. Visser, and M. T. Frankenhuis, 1988. Induction of ascites by low environmental oxygen pressure. Pages 575-579 in: Environment and Animal Health. Proceedings of the 6th International Congress on Animal Hygiene, Skara, Sweden. I. Ekesbo, ed. Sveriges Lantbruksuniversitat, Veterinarmedicinska Fakulteten. Inst. for Husdjurshygien, Skara, Sweden.
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Verstegen, M.WA, W. van der Hel, H. A. Brandsma, A. M. Henken, and A. M Bransen, 1987. The Wageningen respiration unit for animal production research: a description of the equipment and its possibilities. Pages 21-49 in: Energy Metabolism of Farm Animals with Special Reference to Effects of Housing, Stress and Disease. M.W.A. Verstegen and A. M. Henken, ed. Martinus Nijhoff, Dordrecht, The Netherlands. Wethli, E., and JJPS. Wessels, 1973. The relationships among thyroid gland activity, feed intake, mass gain, feed conversion and final body mass in growing chicks. Agroanimalia 5:71-82.
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1991 Poultry Science 70:1069-1083 INTRODUCTION
Ascites refers to the accumulation of edematous fluid within the abdominal cavity. This disease is related to other symptoms having the collective name of "heart failure syndrome" (HFS). Heart failure syndrome comprises abnormalities such as hypertrophy of the heart, especially of the right ventricle, dilation of the heart and hydropericardium, and congested and edematous lungs, as was found by Olander et al. (1967) and Burton et al. (1968). Van der Hel et al. (1988) showed that pathogenic abnormalities in hypoxic broilers exposed to a decreased partial oxygen pressure of 152 millibar (mb) were comparable with those related to ascites, observed in Dutch poultry farms. Huchzermeyer (1984) and Julian (1987) mentioned various factors and agents which contribute to the occurrence of aggravation of ascites and HFS such as salt in feed, furazolidone, plant poisons, and other toxins affecting blood pressure and function of liver, heart, and lungs. Studies concerning the relationship
Royal Zoological Society, Natura Artis Magistra, Amsterdam, The Netherlands. Agricultural Mathematics Group, Wageningen, The Netherlands.
between low partial oxygen pressures at high altitudes and "high altitude disease" provide background data on conditions leading to the development of heart failure and ascites in birds. Generally, avian species are more tolerant to high altitudes than are mammalian species (Schmidt-Nielsen, 1983). Domestic poultry are an exception. Atland (1961) found that chickens had a much lower altitude tolerance than other small warm-blooded animals previously studied. Low partial oxygen pressures resulting in oxygen deficiency or hypoxia leads to tissue oxygen deprivation or anoxia. The low hypoxia resistance of chickens is related to their relatively low hematocrit values, low oxygen-carrying capacity (Rostorfer and Rigdon, 1947), and to the inefficient oxygenation of the fowl lung (Sykes, 1960). Grover et al. (1983) found in an isolated rat lung that acute and chronic hypoxia had an important influence on pulmonary vasomotor tone. Regional reductions in alveolar O2 tension constricted the nearby arterioles. This prevented the return of poorly oxygenated blood to the left atrium by exploiting primarily the better ventilated alveoli. The same adjustment of the regional pulmonary circulation to differences in oxygen tension was found in the duck by Scheid and Holle (1978). Li such a
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ABSTRACT Male broilers of two genetically related stocks with divergent growth rates and feed conversion ratios were used to study metabolic backgrounds on the occurrence of pulmonary hypertension, heart failure, hypoxemia, and ascites in poultry. An experiment with a 2 x 2 x 2 x 2 factorial split-plot arrangement of treatments with 96 groups of 12 broilers was performed. Effects of stock and environmental factors such as ambient temperature, dietary fat, and dietary energy on performance, energy metabolism, oxygen consumption, hematocrit values, and mortality were investigated in broilers from 1 to 5 wk of age. Dissimilar responses of the two stocks to environmental factors reflected genotype by environment interactions and revealed metabolic disorders related to heart failure and ascites. The results indicated that in the stock with the lower feed conversion ratio, a fast protein accretion was achieved together with a reduced ability to convert chemical energy to metabolic heat and to deposit body fat directly from ingested fat Birds with a low feed conversion ratio show less flexibility in metabolic adaptation to a changing environment, which can account for the development of ascites. {Key words: broiler strains, metabolism, feed conversion ratio, dietary factors, ascites)
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incidence of high altitude disease, resulting in pulmonary arterial hypertension, right ventricular hypertrophy, heart failure, hydropericardium, edema in lungs, and ascites in mammals and birds was described by Alexander et al. (1960), Burton et al. (1968), Cueva et al. (1974), and Sillau et al. (1980). More recently, similar symptoms with high mortality rates were observed in broilers at altitudes lower than 2,000 m (Van Blerk, 1985) and even at sea level (Julian et al., 1987; 1989; Scheele and Frankenhuis, 1989). These studies indicated that factors other than a decreased oxygen pressure can create hypoxic conditions in fast-growing meat-type chickens. A low environmental temperature, stimulating the metabolic rate and causing an increased oxygen requirement, had a marked effect on the incidence of HFS and ascites. Julian et al. (1987) indicated that rapidly growing broilers are more susceptible to increased pulmonary arterial pressure than slowly growing broilers. Fast-growing chickens might exhibit elevated metabolic rates and a faster blood flow together with higher oxygen requirements. As a result, the mechanism of pulmonary vasoconstriction, which functions to improve the oxygen saturation of the systematic arterial blood and the increased work load of the heart, could have reached a critical level. A continuing genetic and nutritional improvement in growth rate therefore may result in an increased incidence of HFS and ascites. Modern selection programs deal with a decreased feed conversion ratio (FCR). A better FCR can be obtained by reducing fat deposition in favor of increased protein accretion and by reducing energy requirements for maintenance. When combined with a considerable accumulation of water, protein accretion saves more feed energy than fat accretion does. Solun et al. (1972) showed that a lowered thyroid hormone production in farm animals, which is related to a reduced intensity of cell oxidation, and a diminished oxygen requirement, resulted in a low FCR. Wethli and Wessels (1973) confirmed mese relationships, and reported a tendency toward a low thyroid activity in chickens exhibiting a low FCR. Oxygen consumption is important with respect to HFS and ascites. Therefore, the results of investigations of Stewart et al. (1980) and Stewart and Muir (1982) with different populations of chickens selected for
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reduced pulmonary vascular bed, the heart has to respond by a more vigorous contraction to overcome the higher flow resistance. The inverse proportionality between flow resistance and the fourth power of the flow diameter accentuates the effect of pulmonary vasoconstriction, reducing directly the flow passage diameter, on the increased workload of the heart. Studies of Rosse and Waldmann (1966) showed that anoxia in birds stimulated red blood cell production, resulting in higher hematocrit values. Fahraeus and Lindqvist (1931), and Levy and Share (1953) found a direct relationship between hematocrit values and blood viscosity, which in turn is directly proportional to the flow resistance. A severe pulmonary vasoconstriction combined with increased hematocrit values in hypoxic chickens was found by Cueva et al. (1974) and Sillau et al. (1980). Heart insufficiency and heart failure succeeded pulmonary arterial hypertension and right ventricular hypertrophy in birds that died at high altitudes. Symptoms included a severe thickening of the atrioventricular valve and a general passive congestion in heart, lungs, and liver, accompanying ascites. Heart insufficiency and decreased cardiac output has further consequences. Levy (1979) demonstrated that a stepwise decrease in the output of the right ventricle resulted in a substantial rise of the venous pressure, including the portal vein and hepatic veins, which collect the interstitial fluid from the abdominal cavity. The incidence of edema and ascites in hypoxic fowl can be explained as follows. The transfer of fluid across the thin capillary walls in lung and liver is enhanced by higher resistance and pressure in the arterioles. The reabsorption of the interstitial fluid by the post capillary venules and the drainage capacity of the lympathic vessels can be severely blocked by a heightened venous pressure as a result of heart insufficiency. Such a disturbance in the delicate balance of fluids entering and exiting across the capillary walls will finally result in edema in lungs, hydropericardium, and ascites. Air sacs located in the abdominal cavity are of great importance in regulating the air flow rate entering and leaving the avian lung (Akester, 1978). By inhibiting the action of these air sacs ascites could further intensify hypoxic conditions leading to death. The
ASCITES IN BROILERS
MATERIALS AND METHODS
Chickens Chickens of two genetic groups were used: 1) a pure broiler sire population (SS),3 primarily selected for a favorable FCR combined with a high BW gain; and 2) a commercially available broiler cross (BC)3 in which SS was one of the grandparental populations.
received a standard broiler diet containing 13.4 MJ 4 ME and 215 g CP per kilogram. All chicks were spray vaccinated against Newcastle disease with the La Sota strain at 6 days of age. Experimental Period The experiment lasted from 1 through 5 wk of age. At 1 wk of age, birds from one T a treatment and stock (a flock) separately were divided into six weight classes (52 birds per class). Twentysix groups of 12 birds were formed from each flock by randomly taking 2 birds from each weight class making one group. From each flock, 2 of the 26 groups were killed by carbon dioxide inhalation and prepared for chemical analysis; these two groups served as reference groups in the energy balance measurements. The remaining 96 groups of 12 birds were placed in 96 battery cages (1 x .6 m) on raised wire floors arranged in four climatic rooms, three tiers, and eight cages. Temperature Regimens and Environment Starting at 1 wk of age, two experimental T a were used: a cold T a distinctly below the zone of thermoneutrality of these chicks during the experimental period (T a low) and a normal rearing T a for that period (T a high). The birds raised at a pretreatment regimen of 33 to 30 C were exposed to a regimen of 30 to 22 C (T a high) and those raised at 30 to 25 C were exposed to a regimen of 25 to 15 C (Ta low). During the period from 1 to 5 wk of age, the ambient temperatures were gradually reduced once a day. Relative humidity was kept constant at 60% for both T a regimens. Continuous light was given during the first 3 days in the batteries. After this time, a light regimen of 1 h light and 2 h of darkness was applied. Diets
The dietary experimental factors applied were energy and fat content. Two AME levels The two stocks were raised at two ambient (low and high) and two fat levels (low and high) temperature (Ta) regimens from 0 to 1 wk of age. were used, making four different diets. The The T a was gradually reduced, once a day, from diets, fed in mash form, were composed of 30 to 25 C and from 33 to 30 C, respectively, for normally available feed ingredients such as each regimen. During this period, all chicks maize, maize starch, maize gluten meal, maize gluten feed, wheat middlings, sugar, soybean meal, full fat soybeans, soybean oil, fish meal, sunflower meal, synthetic lysine and methio^uribrid BV, 5831 JN Boxmeer, The Netherlands. 4 nine, limestone, and commercial mineral and 1 MJ = 239 kcal.
Preliminary Period
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high and low O2 consumption supplied most interesting facts. Selection for low oxygen consumption resulted in a significantly better FOR and in a faster-growing and leaner bird. From these results the hypothesis postulated in this study was that a genetic improvement in FCR, in growth rate, and in protein to fat ratio, at least in some populations, might be correlated witii a reduced ability to consume oxygen. Environmental factors such as a low ambient temperature can stimulate the metabolism and increase the oxygen requirement. In these circumstances such birds will approach their long term metabolic limit (Scheele and Frankenhuis, 1989). This could initiate pulmonary hypertension and polycythemia, producing the same cardiac events and edema as occurs under conditions of high altitude. The objective of the present research was to study effects of ambient temperature, energy density of diets, and dietary fat content as factors used to stimulate metabolism in male broilers of two genetically related populations with divergent growth rates and FCR. Dissimilar responses of these populations to the stimulating factors could reflect genotype by environment interactions, revealing metabolic disorders related to HFS and ascites. The present study provides values for performance, energy metabolism, oxygen consumption, and hematocrit values at different ages during an experiment of 4 wk duration.
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SCHEELE ET AL. TABLE 1. Nutrient composition, heat of combustion, AME, AMEn, fat digestibility, and fat energy in AME determined in the experimental diets High AME
Low AME
Measurement
Low fat (Diet 1)
High fat (Diet 2)
Low fat (Diet 3)
High fat (Diet 4)
Protein (N x 6.25), g/kg DM Fat, g/kg DM Crude fiber, g/kg DM Heat of combustion, M^/kg DM AME, MJ/kg DM AME,,, Ml/kg DM Fat digestibility, % Fat energy in AME, %
266 64 19 19.39 15.84 15.03 91.6 14.4
264 169 34 21.47 16.15 15.31 91.8 37.4
246 51 32 18.93 14.39 13.67 90.3 12.5
238 139 53 20.68 14.42 13.69 90.8 34.1
'1 MJ = .239 Meal.
Measurements Feed intake and BW per cage were measured weekly. Deaths were recorded daily and all dead birds were necropsied. At 2, 3, 4, and 5 wk of age, blood samples were collected by venipuncture from one bird per cage. These birds were chosen randomly with the exception that no bird was sampled twice. Hematocrit (Ht) values were measured after centrifugation of the blood as a volume percentage. The AME, AMEn, and digestibility of the fat of the four diets were measured during the 4th wk of age for all cages in the middle tiers of the four climate rooms, according to Scheele and Jansen (1972). The energy retention (RE), protein deposition (RP), and fat deposition (RF) from 1 to 5 wk was measured according to the
comparative slaughter method (Scheele and Jansen, 1972). At 5 wk of age, the body composition was determined in a pooled sample of five randomly chosen chickens from each cage and compared with that of the birds corresponding in stock and T a treatment killed at 1 wk of age. The AME consumption of these five birds per cage was calculated by multiplying the mean FCR per kilogram of BW per cage by the AME value of the diet and by the total BW of the five birds taken for carcass analyses. The mean daily heat production (Hp) per chicken per cage from 1 to 5 wk of age was calculated by subtracting the mean daily RE from the mean daily AME intake (MEj). Verstegen et al. (1987) presented a simple equation to calculate Hp sufficiently accurate from either carbon dioxide production or oxygen consumption (OXc), using a fixed value for the respiratory quotient (RQ). In this experiment OXc (L) was calculated from Hp (kJ) according to the following simplified equation using a RQ of .90: Hp = 20.70 OX^ or OXc = .048 Hp; where MEj, RE, and OXg were calculated per day per unit of metabolic body weight (W*). W* = (Mean BW in kilograms per cage at 5 wk + mean BW in kilograms per cage at 1 wk)/2-75. The main effects and two factor interactions will be discussed. Least significant differences based on two sided tests ( a = .05) were calculated according to Satterthwaite (1946). Statistical Analysis An experiment with a 2 x 2 x 2 x 2 factorial split-plot arrangement of treatments was performed to investigate the effects of ambient temperature regimen (low or high), stock (BC,
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vitamin mixtures. For the digestibility experiments . 1 % Cr2C>3 was added as a marker. Low fat diets contained mainly carbohydrates with low crude fiber contents. In high fat diets, these carbohydrates were exchanged isoenergetically by soybean oil together with low energy feedstuffs containing considerable amounts of crude fiber. Differences in dietary crude fiber contents were also created using two AME levels. In this way crude fiber contents were not automatically connected with fat contents. Effects of crude fiber therefore could be separated from effects of dietary fat. The calculated ratios of CP, lysine, and methionine plus cystine to megajoules of A M E Q in 1 kg feed were 17, .97, and .73, respectively, for all diets. The determined chemical and digestible nutrient composition of the diets is given in Table 1.
ASCITES IN BROILERS
RESULTS
Dietary Parameters Table 1 shows the results of the chemical and physical analyses of the diets and the determined values for the AME—the AME,, as used in feeding tables. Also given are the digestibility coefficients of dietary fat and the percentage of fat energy in the AME. Because the experimental factors of broiler stock and ambient temperature did not show any significant effect (P>.05) on measured AME or fat digestibilities, only mean values are given for each diet. Performance Data and Hematocrits In Table 2, the probability values of significance tests of effects of T a , stock, dietary energy, and dietary fat, and their interactions on performance data and hematocrits at different ages are given. Means of performance data as affected by main factors are shown in Table 3. Body weight gain was clearly effected by stock, dietary AME (P<.001), and fat (P<.05) content
at all ages. The SS birds, the high AME level, and the low fat content in the diets had a positive effect on BW gain. Feed intake was significantly affected by T a (P<.05) and by AME and fat (P<.001) at all ages (Tables 2 and 3). A low T a , a low AME diet containing large amounts of crude fiber, and a low fat diet containing little crude crude fiber increased feed intake. No main effect of stock on feed intake was found. This resulted in a strong effect of stock on FCR. The SS birds showed a better FCR than the BC birds during the entire experimental period. Generally, a low feed intake was accompanied by a low FCR (Tables 2 and 3). Consequently, a high AME and high fat content had a positive effect (P<.001) on FCR. The positive effect of a high T a on FCR increased with age. Significant effects (P<.05) of T a on Ht values were found at 2 and 5 wk of age (Tables 2 and 4). Stock had an increasing effect on Ht values with age, with differences being significant at 3 wk (P<.05) and highly significant at 4 and 5 wk (P<001). Effects of dietary energy and fat on Ht values were only significant (P<.05) at the end of the experimental period at 4 and 5 wk of age, respectively. At different ages, distinctly higher Ht values were found at a low T a and in SS birds (Table 4). Interactions Between Stocks and Ambient Temperatures Some important and highly significant interactions between stocks and T a on performance traits were found (Tables 2 and 5). The effect of T a on BW gain at 3, 4, and 5 wk of age was highly dependent on stock. The low T a stimulated BW gain of the BC broilers but affected BW gain negatively in the SS stock. Also, the effect of T a on feed intake was significantly (P<001) dependent on stock (Tables 2 and 5). As the low T a was clearly below the zone of mermoneutrality for these chickens (Scheele et al., 1987), the BC broilers demonstrated a normal reaction at the low T a by a distinctly increased feed intake compared with intake at the high T a . However, the reaction of the SS broilers on the low T a was strikingly different. Compared witii die BC, die SS broilers only slightly increased feed intake in the cold environment, indicating tiiat these birds were not able to consume sufficiently more energy to produce die extra heat demanded by the cold environment. Consequently, die BW gain of me
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SS), dietary fat (low or high), and dietary energy (low or high). Each temperature regimen was replicated twice. The regimens were randomly assigned to four climate rooms. Within each climate room the eight factorial combinations of stock, dietary fat, and dietary energy were randomly assigned to the eight cages within each tier. Performance data, hematocrits, and energy parameters were analyzed by ANOVA using the model: Yjjkinu,=|J.+T} + ejj + e ljk + Sj + F m + EQ + interactions + e^onm; where Y = observed value of the parameter to be analyzed; \i is the common mean; T, is the effect of the i"1 temperature regimen; Si is the effect of the 1th strain; F m is the effect of the nr* dietary fat level; F^ is the effect of the ifi dietary energy level; interactions stand for all interactions between 2, 3, and 4 factors; eij, ejjfc, and qjkinu, are random errors for climate rooms, tiers within rooms, and cages within tiers, respectively. These random errors were assumed to be independently and normally distributed with variances of a 2 room, a 2 tier, and a 2 cage, respectively. The effect of temperature regimen was tested by using the mean square error for rooms, based on 2 df. The remaining effects and interactions were tested by using die mean square error for cages within tiers based on 70 df.
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SCHEELE EI AL.
TABLE 2. Probability values of significance test of main effects and interactions among experimental factors1 on performance traits and hematocrit values in broilers at different ages Experimental period 1 1 1 1
to to to to
2 3 4 5
wk wk wk wk
1 1 1 1
to to to to
2 3 4 5
wk wk wk wk
1 1 1 1
to to to to
2 3 4 5
wk wk wk wk
2 3 4 5
wk wk wk wk
Ta
*
T a X E Ta X F S x E • Body weight gain (grams per bird per d.inrt y)
Stock (S)
AME, (E)
Fat, (F)
T,xS
*** ***
*** *** *** ***
* * * *
** *** ***
**+
***
S x F
E x F
** **
** * *
Feed intake (grams per bird per day)
* ** ***
** *** *** ***
* *
* *
* **
Feed conversion ratio (g:g)
*** *** *** ***
*** *** *** *+*
** *** *** ***
* *** ***
*
*
**
*** *** *
** ** ***
* *
*
. . .
1 T a =two ambient temperatures; Stock=two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broiler cross (BC) in which SS was one of the grandparental lines; AME, and dietary fat (fat) both at low levels. *P<05. **P<.01. ***P<.001.
TABLE 3. Mean values for body weight gain, feed intake, and feed conversion ratio of broilers at different ages as affected by experimented factors1
Low
period
High
BC
to to to to
2 3 4 5
wk wk wk wk
234 611 1,062 1,520
229 611 1,079 1,524
225 594 1,039 1,479
1 1 1 1
to to to to
2 3 4 5
wk wk wk wk
301 857 1,621 2,518
286 814 1,543 2,393
293 832 1,576 2,449
1 1 1 1
to to to to
2 3 4 5
wk wk wk wk
1.25 1.33 1.43 1.57
Low
SS
1 1 1 1
1.29 1.40 1.53 1.66
AME
Stock
T *a
1.30 1.40 1.52 1.66
- Body weight gain (g) 226 238 628 601 1,102 1,054 1,565 1,494 Feed intfllr** t**\ 294 300 838 857 1,624 1,589 2,461 2,521 1.24 1.34 1.44 1.57
1.33 1.43 1.54 1.69
Fat
High
Low
High
237 620 1,088 1,550
238 628 1,093 1,545
225 593 1,048 1,499
287 813 1,541 2,389
307 875 1,642 2,526
280 796 1,522 2,384
1.21 1.31 1.42 1.54
1.30 1.39 1.50 1.64
1.24 1.34 1.46 1.59
! T a =two ambient temperatures; Stock=two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broilerCTOSS(BC) in which SS was one of the grandparental lines; AME, and dietary fat (fat) both at low levels.
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*** *** *** ***
* * * *
ASCITES IN BROILERS
1075
TABLE 4. Mean hematocrit values of broilers at different ages as affected by experimental factorr Stock
Fat
AME
Age
Low
High
SS
BC
2 3 4 5
30.4 31.1 32.9 32.7
28.5 29.4 31.1 29.4
29.6 31.1 33.7 32.3
29.3 29.4 30.3 29.7
Low
High
Low
High
29.7 29.9 31.0 30.5
29.3 30.6 32.9 31.5
29.5 30.3 32.0 30.3
29.5 30.2 32.0 31.7
CWl wk wk wk wk
*Ta=two ambient temperatures; Stock=two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broiler cross (BC) in which SS was one of the grandparental lines; and AME, and dietary fat (fat) both at low levels.
Interactions Between Dietary Fat Content and Other Experimental Factors Effects of dietary fat on the performance of the broilers were significantly dependent on T a and stock, as is shown in Tables 2 and 6. It is important to note that interactions between dietary energy and T a or stock differed among the cases. This indicated that the effects of dietary fat in the interactions were mainly independent of effects of dietary crude fiber. In
TABLE 5. The significant (P<.05) interactions between stockr and ambient temperature on performance data and hematocrit values of broilers at different ages Stock x Ta SS
BC
Experimlental period
Low Ta
High Ta
Low T a
High T a
LSDx2
LSD 2 3
1 to 3 wk 1 to 4 wk 1 to 5 wk
600 1,044 1,498
589 1,034 1,460
622 1,080 1,542
633 1,124 1,587
12 22 35
18 17 38
304 867 1,645 2,561
282 798 1,507 2,337
7 16 32 57
14 32 34 51
1 1 1 1
to to to to
2 3 4 5
wk wk wk wk
1 1 1 1
to to to to
2 3 4 5
wk wk wk wk
4 wk
1.33 1.45 1.58 1.71 30.2
1.28 1.36 1.46 1.60 30.3
298 290 846 830 1,598 1,579 2,474 2,448 - Feed conversion ratio (g:g) — 1.25 1.36 1.48 1.61 35.6
1.23 1.31 1.41 1.54 31.8
.01 .01 .01 .02 2.1
.02 .04 .02 .01 3.1
'T, = two ambient temperatures; Stock = two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broiler cross (BQ in which SS was one of the grandparental lines; AME and dietary fat (fat) both at low levels. LSDj = least significant difference comparing two means within the same Ta regimen. = least significant difference comparing two means with different Ta regimens.
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SS birds, in contrast to the BC birds, was negatively affected by the low T a . The relatively low level of feed intake of SS birds at a low T a is also reflected in the interaction of stock and T a on FCR (Tables 2 and 5). Due to the rather constant feed intake, FCR of the SS birds increased only slightly at a decreased T a , but this was clearly different from the BC birds. At 4 wk ofage, the effect of T a on Ht values was strongly dependent on stock. The SS birds probably had a shortage of oxygen consumption at a low T a .
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SCHEELE ET AL. TABLE 6. The significant (P<.05) interactions of dietary fat1 with ambient temperature, with stock, and with dietary AME, on performance data of broilers at different ages Fat x T a High fat
Low fat
Experinilental period
Low T a
High T a
Low T a
High T a
LSDj 2
LSD 2 3
1 to 3 wk 1 to 4 wk 1 to 5 wk
635 1,094 1,558
621 1,092 1,533
587 1,030 1,483
600 1,066 1,515
12 22 35
18 17 38
1 to 2 wk 1 to 3 wk
317 902
297 847
285 811
275 780
7 16
14 32
1.41 1.54 1.67
1.39 1.52 1.65
1.37 1.47 1.61
1.30 1.40 1.54
.01 .01 .02
.04 .02 .01
Fat x stock Low fat BC
High fat BC
SS
SS
1 to 2 wk 1 to 3 wk
228 606
248 651
222 583
228 604
6 12
1 to 2 wk 1 to 3 wk
304 865
311 884
282 800
278 792
6 16
1 to 2 wk
1.34
1.27
1.26
1.22
.01
Fat x AME High fat
Low fat Low AME 1 to 2 wk 1 to 3 wk 1 to 4 wk
1.34 1.44 1.56
High AME
Low AME
1.25 1.34 1.45
1.32 1.41 1.52
High AME 1.17 1.28 1.39
.01 .01 .01
T",=two ambient temperatures; Stock=two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broiler cross (BQ in which SS was one of the grandparental lines; AME and dietary fat (fat) both at low levels. LSDx = least significant difference comparing two means within the same temperature regimen. \SI>2 = least significant difference comparing two means with different T a regimens.
periods 1 to 3,1 to 4, and 1 to 5 wk of age the fat by T a interaction was clearly affecting BW gain, In these periods the combination of low T a and high fat had a marked detrimental influence on BW gain. With the low fat diets, a low T a had a fi o*;m,Tw; ~te * nnr • W stimulating effect on BW gam. By lowering T a , the increase in feed intake was less with the high than with the low fat diet (Tables 2 and 6). The birds seemed to be inhibited from consuming more feed if the diets
contained a high quantity of fat. These results indicated that chickens had problems metabolizm g i^gg quantities of dietary fat. The notably ^ ^ F C R a t a Ugh fat content, even when „„, . . 7 « . j ., w gain was reduced, was affected greatly by , . , . , . , , , . , _ . „ 7 , , me "**>tod feed intake. Especially in the last weeks, the effect of an increased fat content on FCR was much greater at a high T a than at a low Ta.
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1 to 3 wk 1 to 4 wk 1 to 5 wk
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ASCITES IN BROILERS
Mortality Rates The mortality rate was 4.5%. Heart failure syndrome and ascites were the most important causes of death. Deaths related to experimental factors are shown in Table 7. Table 7 also lists numbers of dead birds in which no pathogenic abnormalities were found other than HFS or
ascites. From 36 birds with severe symptoms of HFS and ascites, 24 birds belonged to the SS stock kept at a low temperature. Energy Metabolism In Table 8, the probability values of significance tests of effects of the experimental factors on energy metabolism parameters over the period from 1 to 5 wk of age are presented. The means of energy metabolism data for the levels of the experimental factors are given in Table 9. The ME; per unit of metabolic BW was strongly affected by all factors. With the exception of T a , the experimental factors appeared to have marked effects on RE per unit of metabohc B W. The effects of the dietary factors were highly significant (P<.001). The RE per unit of metabolic BW was higher in the BC than in the SS birds. When energy retention is expressed in kilojoules per day per bird, the RE, as well as deposited protein and fat in grams per day per bird, were highest in the SS birds. The ratio of energy deposition to BW gain was different for both stocks. High energy and low fat diets clearly favored RE per unit of metabolic weight. Oxygen consumption was enhanced by a low T a , which was directly related to a higher heat production. High energy and low fat diets showed the highest rate of deposition of protein and fat, which correlates with the higher ME, values with these diets (Tables 8 and 9). Protein deposition, and thus also accumulation of water, was significantly (P<.001) higher in SS birds than in BC birds. Weight gained through water retention is reflected in the better FCR of SS stock. All experimental factors had important effects on the energetic efficiency of the diets for
TABLE 7. Total mortality during the experimental period, and mortality caused by heart failure syndrome (HFS) and ascites (number of birds) Dietary factors Stock
Ta Mortality
Low
High
BC
SS
Low AME
High AME
Low fat
High fat
Total HFS Ascites
37 10 18
15 6 2
14 5 2
38 11 18
30 12 12
22 4 8
28 10 11
24 6 9
T a =two ambient temperatures; Stock=two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broiler cross (BC) in which SS was one of the grandparental lines; AME, and dietary fat (fat) both at low levels.
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At 2 and 3 wk of age, a significant (P<.01) interaction between fat and stock affecting BW gain was revealed (Tables 2 and 6). In these periods, the difference between stocks was markedly more pronounced at the low than the high fat level. The SS broilers obviously could not fully utilize tiieir higher capacity for growth when high fat diets were fed. An interesting difference was found between stocks at 1 to 2 wk and 1 to 3 wk of age in their feed intake response to differences in dietary fat content (Tables 2 and 6). Only with low fat diets did the SS consume significantly (P<.05) more feed than the BC. This indicates that the SS chickens were more sensitive to a high fat content in diets than the BC broilers. Li regard to FCR, the differences between stocks during the first experimental week were significantly (P<.05) greater at a low dietary fat level compared with a high fat content (Tables 2 and 6). The high productive capacity of the SS was reduced when environmental circumstances were less favorable. Another interaction affecting FCR significantly (P<001) was dietary AME by dietary fat level. The beneficial effect of a high fat content on FCR as a result of a lowered feed intake was most pronounced in high energy diets, hi fact, the high fat content prevented an overconsumption of dietary energy, which can happen when highly concentrated diets are fed.
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TABLE 8. Probability values of significance tests of effects of experimental factors^ on AME intake (MEj), energy retention (RE), and oxygen consumption (OXe) all calculated per metabolic weight (W*), on deposited fat (RF) and protein (RP), and on efficiency of MEj for body weight gain (BWGIMEj) in broilers from 1 to S wk of age Variable2 MEj/W* RE/W* OXc/W* RF RP BWG/MEj
Ta
Stock (S) AME, (E) Fat, (F)
*** ***
*** ***
*** ***
*** * ***
***
T,xS
I,xE
T,xF
S x E
S x F
E x F
***
BW gain expressed as BW gain:MEi (Tables 8 and 9). The highest efficiency was obtained at a high T a , from SS birds, with low AME and high fat content in diets. In all these cases, the high efficiencies corresponded to relatively low values for ME}. Interactions Between Factors in Respect to Energy Metabolism The T a factor was involved in all important interactions affecting energy metabolism variables. The highly significant (P<001) effect of
the interaction of T a by stock on MEj per metabolic weight pointed distinctly to the relative low MEj at a low T a of the SS birds compared with the BC birds. At a high T a , SS birds did not consume less energy than BC. Also the effect of the T a by stock interaction on OXc revealed striking differences in metabolism (Table 10). At a low T a , a higher OXc was required in both stocks to meet the increased demand for heat production. But at the same metabolic BW, the OXg at a low T a was significantly (P<.01) lower for the SS than for the BC. At a low T a the SS stock was not able to
TABLE 9. Mean values of AME intake (MEj), energy retention (RE), and oxygen consumption (OXe) all calculated per metabolic weight (W*), of deposited fat (RF) and protein (RP), and of efficiency of MEj for body weight gain (BWG/MEi) in broilers from J to 5 wk of age as affected by experimental factors'
Variable2
Low
MEj/W* RE/W* OXc/W* RF RP BWG/MEi
1,342 565 37.7 7.1 10.1 46.6
Ta High 1,273 590 33.2 7.8 9.9 49.2
AME
Stock
Fat
BC
SS
Low
High
Low
High
1,320 585 35.7 7.6 9.8 46.7
1,295 571 35.1 7.3 10.2 49.1
137 557 35.4 6.9 9.9 48.4
1,328 598 35.4 8.0 10.1 47.4
1,327 598 35.0 8.0 10.1 47.5
1,288 557 35.8 6.9 9.9 48.3
T a = two ambient temperatures; Stock=two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broiler cross (BC) in which SS was one of the grandparental lines; AME, and dietary fat (fat) both at low levels. 2 MEi and RE in kilojoules per day (lkJ = .239 kcal); OX,, in liters per day, W* = mean body weight in kilograms to the power .75, RF and RP in grams per day, BWG/MEj in grams per megajoule.
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4",=two ambient temperatures; Stock=two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a commercially available broiler cross (BC) in which SS was one of the grandparental lines; AME, and dietary fat (fat) both at low levels. 2 ME; and RE in kilojoules per day (lkJ = .239 kcal); OXe in liters per day, W* = mean body weight in kilograms to the power .75; RF and RP in grams per day; BWG/ME; in grams per megajoule. *P<05. **P<01. ***P<.001.
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energetic efficiency BW gain:MEj also was affected by the interaction of T a by dietary fat (P<.001). A beneficial effect of a high dietary fat content caused by a reduced MEj on BW gain: MEj was found only at a high T a . The high dietary fat level reduced ME, noticably less at a low T a . Furthermore, a high fat level resulted in a higher heat expenditure at a low T a . Consequently, at a low T a , no positive effect of a high fat level on BW gain:MEj was found. DISCUSSION
Stimulating the metabolism of two different broiler populations by T a and by dietary factors resulted in dissimilar responses revealing metabolic dysfunctions. Interactions between stock and ambient temperature or dietary fat demonstrated clearly that the SS birds, which were selected primarily for a low FCR, were more sensitive to stimulating factors man the commercial BC birds. The SS birds had difficulty adapting to changes in their environment. Consequently, differences
TABLE 10. The significant (P<.05) interactions of TJ with stock, with dietary AME and with dietary fat on AME intake (ME;), and oxygen consumption (OXc) both calculated per metabolic weight (W*), and on efficiency of MEj for body weight gain (BWG/MEj) in broilers from 1 to 5 wk of age T a x stock High T a
Low T a Variable2
BC
SS
BC
SS
LSD! 3
LSD 2 4
ME/W* OX^/W* BWG/MEi
1,369 38.6 45.1
1,314 36.7 48.1
1,271 32.7 48.4
1,276 33.6 50.1
15 1.3 .6
13 1.3 .5
.6
.5
15 1.7 .6
13 1.7 .5
T a X AME High T a
Low T a Low AME BWG/MEi
46.8
High AME 46.4
Low AME 49.9
High AME 48.5
T8, x fat High T a
Low T a MEj/W*
oxyw* BWG/MEi
Low fat
High fat
Low fat
High fat
1,355 36.8 46.6
1,329 38.6 46.6
1,299 33.2 48.4
1,248 33.0 50.1
1 T a = Two ambient temperatures; stock = two genetic groups of broilers, a pure line primarily selected for a favorable feed conversion ratio (SS) and a comeicially available broiler cross (BC) in which SS was one of the grandparent lines; AME, and dietary fat (fat) both at low levels. 2 MEi in kUojoules per day (lkj = .239 kcal); OX,, in liters per day; BWG/ME; in grams per MJ; W* = mean body weight in kilograms to the power .75. \S0\ = Least significant difference comparing two means within the same T a regimen. 4 LSD 2 = Least significant difference comparing two means with different T a regimens.
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consume enough oxygen to maintain the relatively high metabolic rate compared with the BC, as was demonstrated at a high T a . Consonant with those findings was the effect of the T a by stock interaction on BW gain:MEj. Due to a low heat production rate at a low T a , the relatively high energetic efficiency of the SS for growth differed more from that of the BC at low T a than at high T a . The significant interaction (P<.01) between T a and AME for BW gain:MEi indicated that at a high T a the birds exhibited an overconsumption of dietary energy through high energy diets. The significant (P<.05) interaction between T a and fat in the effect on MEj per metabolic BW means that at a high T a the depressing effect of fat on MEj was more pronounced than at a low T a (Table 10). A significant (P<.05) interaction of T a by dietary fat was found in the effect on OXg. Despite a depressed MEj caused by a high dietary fat level, the heat expenditure at the low T a , and thus the oxygen consumption, were enhanced by that high fat level. As a result the
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SCHEELE ET AL.
Mortality was not high in the present experiment. However, two-thirds of the examined dead birds suffering from HFS or ascites belonged to the SS broilers kept at a low T a . At a low T a , SS birds demonstrated a lower OXg and higher hematocrits relative to the BC broilers. This is in agreement with findings reported by Sillau et al. (1980), Van Blerk (1985), and Van der Hel et al (1988), who related symptoms of heart failure and edema, including ascites and high hematocrits, to a lowered partial oxygen pressure. Notably, the SS birds fed high AME diets showed higher hematocrits in the 4th wk of age. As concentrated diets stimulate metabolism, this interaction between stock and dietary energy level illustrated that SS birds were near their long term metabolic limit. Effects of different dietary AME levels in this experiment were as expected. The high energy diet had a positive effect on BW gain and energy retention. The birds fed the low energy diets tried to compensate by consuming more feed, however, they were not able to eat the same amount of AME per day as birds fed the high AME diets. The latter deposited more fat but only slightly more protein. As a result of the lower MEj, a relatively high level of protein deposition, and a considerable accumulation of water, the birds fed the low AME diets exhibited the highest energetic efficiency for BW gain. In some cases the main effects of low energy diets and of high fat diets were similar. Low energy and high fat diets with relatively high crude fiber contents showed a reduced energy consumption resulting in a lower BW gain and in less deposition of fat. This indicates that a high crude fiber content might have contributed to the effects of these diets. The important differences among effects of low energy and high fat point to the important role of dietary fat per se in this experiment. First, the observed reductions in BW gain and feed intake caused by high fat diets were most pronounced in high energy diets. In high energy diets, crude fiber with maximum contents of 34 g/kg feed was of minor importance. Therefore, the effects of high fat diets indicated that both stocks exhibited problems in either digestion of fat or in lipid metabolism after intestinal absorption. Second, the highly significant interactions between dietary fat and whether stock or ambient temperature illuminated the specific
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in BW gain, feed intake, FOR, Ht values, MEj, OXg, and weight gain:MEj between stocks were markedly dependent on environmental temperature and also on dietary fat level. The relative retardation of BW gain and feed intake and the relatively high Ht values of SS broilers compared with BC birds when metabolism was forced were similar to effects found under hypoxic conditions (Sillau et al, 1980; Van der Hel et al, 1988; Julian et al, 1989). The high Ht values in SS birds at a low T a corresponded very well with the observed low level of OXc per metabolic BW compared with the BC broilers. This result is similar to those reported from experiments under hypoxic conditions, and indicates the inability of the SS birds to adapt metabolically to changes in the environment. The SS chicks hardly increased their feed intake or ME, at the low T a compared with the high T a . As protein gain was not affected by T a , the difference in FCR and in BW gain:MEj between the two stocks was most pronounced at a low T a . Clearly, a high energetic efficiency for growth can have a negative significance when this is connected to a situation of stress. The results indicated that the SS birds grown at the low T a were forced to save energy at the cost of heat production and fat deposition, perhaps because they did not have the capacity for a high rate of combustion of chemical energy. The low heat production rate and low OXg at low temperatures signals inadequate metabolic action. Under unfavorable environmental conditions, this can lead to imbalances resulting in pulmonary hypertension, cardiac hypertrophy, heart failure, hypoxaemia, and finally, to edema resulting in ascites. The results indicated a relationship between a low rate of OX,, and FCR, particularly at a low T a . This confirms the results of Stewart and Muir (1982). Selection for a low FCR may be accompanied by a decreased respiratory exchange, which might be related to an inability to consume sufficient oxygen. This concept is sustained by observations of Huchzermeyer et al (1988), who reported that commercial broiler strains differ in their susceptibility for pulmonary hypertension syndrome. It was concluded that an effective abatement of diseases like ascites could be encouraged by examining the development of relevant metabolic parameters during selection of the domestic fowl on exterior traits like growth rate and FCR.
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and OXg were significantly higher with high fat diets compared wim low fat diets. Obviously, digestion of fat was more than sufficient to deliver the fuel needed for protein synthesis and for combustion to heat. The clearly depressed deposition of body fat by chickens consuming high fat diets reveals problems in the synthesis and retention of body fat. Studies of Leveille et al. (1975), Hillard et al. (1980) and Tanaka et al. (1983) elucidated how a high dietary fat content exerted a depressing effect on hepatic lipid synthesis either by the dietary fat level per se or by the simultaneously decreased carbohydrate level in the diet. Carew and Hill (1964) found that, in spite of such a reduced fat synmesis, the deposition of fat in chicken tissues directly from ingested fat was clearly enhanced as the dietary level of com oil was increased up to 22.5%. Carew et al. (1963) also found beneficial effects of high levels of dietary soybean oil, independent of density of diets, on BW gain of chickens. This is in marked contrast with the results of the present study using low and high levels of soybean oil. Possibly, SS and BC birds have limited abilities to synthesize or to deposit fat, because selection for FCR is correlated wim lower body fat values. During selection for characteristics such as FCR, which will have an impact on metabolism, attention may have to be given to changes in metabolic parameters governing heat production and oxygen consumption (maintenance) and protein and fat synthesis. Only then can a development of undesired pathways in metabolic processes be avoided. The results of the present experiment suggest that in the SS birds, a fast protein gain was achieved together with a reduced ability of converting chemical energy to heat and of depositing fat in tissues directly from dietary fat. Such metabolic reductions point to less flexibility in adaptation of metabolism to a changing environment. Finally, the additive sum of these kinds of stressing factors can account for development of metabolic disorders such as heart failure syndrome and ascites. REFERENCES Akester, A. R., 1978. Microcirculation in birds. Pages 687-735 in: Microcirculation. Vol. 2, Chapter 18. G. Kaley and B. M. Altura, ed. University Park Press, Baltimore, MD.
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role of fat as a source of dietary energy in poultry metabolism. It appeared that die SS chickens were less tolerant of the high fat diets than the BC chicks. At the low fat level, the SS birds exhibited die greater positive difference in BW gain, feed intake, and FCR compared with BC broilers. In these circumstances, the SS birds showed that, relative to the BC birds, they were able to consume large quantities of feed including low energy diets. A striking result was obtained by comparing the SS birds with the BC birds at 3 wk of age when fed diets with a high fat content. The feed intake of tihese SS birds was even less than that of the BC. The negative impact of high dietary fat levels on SS chickens reflected the greater sensitivity of this stock for stressing factors in metabolism. High fat diets primarily resulted in less deposition of fat, protein deposition was only slightly affected, and the overall result was a better FCR. This may indicate that in some cases a favorable FCR can be associated with an inhibition of metabolism, which could cause metabolic disorders. Rand et al. (1958), Renner (1964), and Brambalia and Hill (1966) reported mat the chicken is tolerant of low carbohydrate and high fat diets up to 30% dietary fat. Comparing their results obtained more man 20 yr ago with the present experiment with modern broiler stocks indicates that selection can create birds with less tolerance to high fat diets. At 5 wk of age, increased dietary fat resulted in significantly higher Ht values. Combustion of fat energy to heat requires more oxygen man combustion of carbohydrate energy. Differences in dietary fat interacted importantly with differences in T a . Especially at the low T a the depressing effect of fat on feed intake and ME} and on BW gain was clearly pronounced. When a higher intake was needed because of a higher thermal demand of the environment, the birds fed the high fat diets were not able to consume enough feed to meet their energy requirements for growth. Problems with digesting large quantities of fat could explain the low energy intake within high fat diets. The observed high digestion coefficients of fat (Table 1), in the present experiment, however, point to other causes. At a low T a , even when high fat diets lowered ME;, virtually no effect on protein deposition could be found. Furthermore, heat production
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SCHEELE ET AL. 247-255. Olander, H. J., R. R. Burton, and H. E. Adler, 1967. The pathophysiology of chronic hypoxia in chickens. Avian Dis. 11:609-620. Rand, N. T., H. M. Scott, and F. A. Kumerov, 1958. Dietary fat in the nutrition of the growing chick. Poultry Sci. 37:1075-1085. Rentier, R., 1964. Factors affecting the utilization of carbohydrate-free diets by the chick. I. Level of protein. J. Nutr. 84:322-326. Rosse, W. F., and T. A. Waldmann, 1966. Factors controlling erythropoiesis in birds. Blood 27: 654-661. Rostorfer, H. H., and R. H. Rigdon, 1947. The relation of blood oxygen transport to resistance to anoxia in chicks and ducklings. Biol. Bull. 92:23-30. Satterthwaite, F. E., 1946. An approximate distribution of estimates of variance components. Biometrics Bull. 2:110-114. Scheele, C. W., and M. T. Frankenhuis, 1989. Stimulation of the metabolic rate in broilers and the occurrence of metabolic disorders. Pages 251-255 in: Energy Metabolism of Farm Animals. European Association of Animal Production Publication Number 43. Y. van der Honing and W. H. Close, ed. Pudoc, Wageningen, The Netherlands. Scheele, C. W., W. van der Hel, M.WA. Verstegen, and A. M Henken, 1987. Climatic environment and energy metabolism in broilers. Pages 217-261 in: Energy Metabolism of Farm Animals with Special Reference to Effects of Housing, Stress and Disease. M W A . Verstegen and A. M. Henken, ed. Martinus Nijhoff, Dordrecht, The Netherlands. Scheele, C. W., and B. P. Jansen, 1972. Standardization of nitrogen-balance experiments with rats. 2. Experimental procedure and techniques used in the evaluation of the experiments. Z. Tierphysiol. Tierernahr. Futtermittelkd. 28:24-28. Scheid, P., and J. P. Holle, 1978. Adjustment of the regional pulmonary circulation to the profile of oxygen pressure along the parahronchus in the duck. Pages 105-111 in: Respiratory Function in Birds, Adult and Embryonic. Johannes Piiper, ed. SpringerVerlag, Berlin, Germany. Schmidt-Nielsen, K., 1983. Animal Physiology: Adaptation and Environment Cambridge University Press, New York, NY. Sillau, A. H., S. Cueva, and P. Morales, 1980. Pulmonary arterial hypertension in male and female chickens at 3300 m. Pflugers Archiv. Eur. J. Physiol. 385: 269-275. Solun, A. S., L. M. Yakimenko, V. L. Mikhailov, L. N. Selivanova, and Z. A. Tkachek, 1972. Ispol'zovanie khlomokislogo ammoniya pri otkorme sel'skokhozyaistvennykh zhivotnykh. Khim. Sel'sk. Khoz. 10:925-931. Stewart, P. A., and W. M. Muir, 1982. The effect of varying protein levels on carcass composition and nutrient utilization in two lines of chickens divergently selected for Oj consumption. Poultry Sci. 61: 1-11. Stewart, P. A., W. M. Muir, J. J. Begin, and T. H. Johnson, 1980. Feed efficiency and gain responses to protein levels in two lines of birds selected for oxygen consumption. Poultry Sci. 59:2692-2696. Sykes, A. H., 1960. A note on the determination of oxygen in the blood of the fowl. Poultry Sci. 39:16-18. Tanaka, K., S. Ohtani, and K. Shigeno, 1983. Effect of
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on May 30, 2015
Alexander, A. F., D. H. Will, R. F. Grover, and J. T. Reeves, 1960. Pulmonary hypertension and right ventricular hypertrophy in cattle at high altitude. Am. J. Vet. Res. 21:199-204. Atland, P. D., 1961. Altitude tolerance of chickens and pigeons. J. Appl. Physiol. 16(1):141-143. Brambila, S., and F. W. Hill, 1966. Comparison of neutral fat and free fatty acids in high lipid-low carbohydrate diets for the growing chicken. J. Nutr. 88:84-92. Burton, R. R., E. J. Besch, and A. H. Smith, 1968. Effect of chronic hypoxia on the pulmonary arterial blood pressure of the chicken. Am. J. Physiol. 214: 1438-1442. Carew, L. B., and F. W. Hill, 1964. Effect of corn oil on metabolic efficiency of energy utilization by chicks. J. Nutr. 83:293-299. Carew, L. B., M C. Nesheim, and F. W. Hill, 1963. The relationship of dietary energy level and density to the growth response of chicks to fats. Poultry Sci. 42: 710-718. Cueva, S., H. Sillau, A. Valenzuela, and H. Ploog, 1974. High altitude induced pulmonary hypertension and right heart failure in broiler chickens. Res. Vet. Sci. 16:370-374. Fahraeus, R., and T. Lindqvist, 1931. The viscosity of the blood in narrow capillary tubes. Am. J. Physiol. 96: 562-568. Grover, R. F., W. W. Wagner Jr., I. F. MacMurtry, and J. T. Reeves, 1983. Pulmonary circulation. Pages 103-106 in: Handbook of Physiology, Section 2: The Cardiovascular System-Peripheral Circulation and Organ Blood Flow. Vol. EI. Am. Physiol. Soc, Bethesda, MD. Hillard, B. L., P. Lundin, and S. D. Clarke, 1980. Essentiality of dietary carbohydrate for maintenance of liver lipogenesis in the chick. J. Nutr. 110: 1533-1542. Huchzermeyer, F. W., 1984. Waterbelly. Altitude disease. Poult. Bull. (June):279-281. Huchzermeyer, F. W., A.M.C. de Ruijck, and H. van Ark, 1988. Broiler pulmonary hypertension syndrome ID. Commercial broiler strains differ in their susceptibility. Onderstepoort J. Vet. Res. 55:5-9. Julian, R. J., 1987. The effect of increased sodium in the drinking water onrightventricular hypertrophy, right ventricular failure and ascites in broiler chickens. Avian Pathol. 16:61-71. Julian, R. J., G. W. Friars, H. French, and M. Quinton, 1987. The relationship of right ventricular hypertrophy, right ventricular failure and ascites to weight gain in broiler and roaster chickens. Avian Dis. 31: 130-135. Julian, R. J., I. McMillan, and M. Quinton, 1989. The effect of cold and dietary energy on right ventricular hypertrophy, right ventricular failure and ascites in meat-type chickens. Avian Pathol. 18:675-684. Leveille, G. A., D. R. Romsos, Y. Y. Yen, and E. K. O'Hara, 1975. Lipid biosynthesis in the chick. A consideration of site of synthesis, influence of diet and possible regulatory mechanisms. Poultry Sci. 54: 1075-1093. Levy, M. N., 1979. The cardiac and vascular factors that determine systematic blood flow. Circ. Res. 44: 739-746. Levy, M. N., and L. Share, 1953. The influence of erythrocyte concentration upon the pressure-flow relationships in the dog's hind limb. Circ. Res. 1:
ASCITES IN BROILERS increasing dietary energy on hepatic lipogenesis in growing chicks, n. Increasing energy by fat or protein supplementation. Poultry Sci. 62:452-458. Van Blerk, S., 1985. Changing disease picture for broilers. Poult. Int. (December): 19-24. Van der Hel, W., A. M. Henken, J. Visser, and M. T. Frankenhuis, 1988. Induction of ascites by low environmental oxygen pressure. Pages 575-579 in: Environment and Animal Health. Proceedings of the 6th International Congress on Animal Hygiene, Skara, Sweden. I. Ekesbo, ed. Sveriges Lantbruksuniversitat, Veterinarmedicinska Fakulteten. Inst. for Husdjurshygien, Skara, Sweden.
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Verstegen, M.WA, W. van der Hel, H. A. Brandsma, A. M. Henken, and A. M Bransen, 1987. The Wageningen respiration unit for animal production research: a description of the equipment and its possibilities. Pages 21-49 in: Energy Metabolism of Farm Animals with Special Reference to Effects of Housing, Stress and Disease. M.W.A. Verstegen and A. M. Henken, ed. Martinus Nijhoff, Dordrecht, The Netherlands. Wethli, E., and JJPS. Wessels, 1973. The relationships among thyroid gland activity, feed intake, mass gain, feed conversion and final body mass in growing chicks. Agroanimalia 5:71-82.
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