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Processing Yields as Affected by Dietary Potassium Chloride Concentration and Energy Level in Summer and Winter1
MARKETING AND PRODUCTS Processing Yields as Affected by Dietary Potassium Chloride Concentration and Energy Level in Summer and Winter1 D. M. JANKY, R. H. HARMS, and A. S. ARAFA Department of Poultry Science, University of Florida, Gainesville, Florida 32611 (Received for publication September 20, 1982)
1983 Poultry Science 62:1998-2003 INTRODUCTION
It has long been recognized that environmental factors, especially temperature, have an effect on broiler production, mainly through decreased efficiency and increased costs. Due to escalating energy costs, the use of environmentally controlled housing in the Southeast may not solve these decreased efficiency problems within practical costs. In the Southeast, the temperature problem of most severity would appear to be excessive heat rather than excessive cold. Severe heat may cause heat prostration, death, or inefficient growth, especially in unacclimated broilers (Reece et al., 1972). The effects of heat on broilers could be more subtle, such as decreasing yields through excessive shrink due to evapotranspiration during preslaughter holding. Previous studies have indicated that energy level of the diet (Janky et al, 1976) and the addition of an electrolyte such as potassium chloride (KC1) (Riley et al, 1976) have an effect on ready-to-cook broiler yields. In these studies, numerical trends in ready-to-cook yields were observed that indicated an environ-
1
Florida Agricultural Experiment Stations Journal Series No. 4123.
mental interaction with dietary energy level, or electrolyte administration, or both. The purpose of these experiments was to clarify the relationship of dietary energy level and KC1 supplementation to broiler yields, shrink, and water uptake as affected by environmental temperature. EXPERIMENTAL PROCEDURE
In each of two experiments, 20 (10 male, 10 female) day-old Cobb color-sexed broilers were assigned to each of three pens (2.3 m ' ) contained in four experimental houses. The four houses were identical and were equipped with shuttered east and west windows. The four experimental houses are small (9.2 m 2 ) and located in an east-west line 32 m apart. All houses are subjected to the same amount of sun, wind, and other environmental conditions. In previous experiments in these houses, there have been no housing or housing x treatment effects on body weights or feed efficiencies. Due to these factors, each pen in each house was assumed to provide an identical environment to the other pens within the house and to the pens located in the other three houses. Broilers were fed a standard starter diet and reared on peanut-hull litter using a continuous lighting regimen supplemented with thermostatically-controlled infrared brooding lamps
1998
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ABSTRACT Equal numbers of male and female Cobb color-sexed broilers (28 days of age) were fed finisher diets containing 2665, 3056, or 3 335 kcal ME/kg of diet. One-half of the birds on each dietary energy treatment were fed .75% potassium chloride (KC1) the last 5 days prior to slaughter. The experiments were conducted in winter (Feb to Mar) and in summer (Jul to Aug). Birds were processed and various yield parameters calculated. Raw ready-to-cook carcass composition was also determined. During winter, decreasing dietary energy level significantly decreased percent yield due to increased shrink. The addition of KC1 to the diet in winter had no effect on yield characteristics and composition was affected only slightly by KG treatment. In summer, percent shrink was significantly decreased as dietary energy level was decreased, whereas water uptake was significantly increased. This resulted in no dietary energy effect on ready-to-cook yield. Adding KC1 to the diet in summer increased ready-to-cook yield by decreasing shrink. Fat was increased as dietary energy level was increased in both summer and winter. Moisture was inversely related to fat. (Key words.- energy, yields, broiler, seasonal variation, potassium chloride)
BROILER YIELDS: POTASSIUM CHLORIDE, ENERGY, OR SEASON
daily maximum ranged from 10.0 to 28.9 C and the average daily minimum ranged from —2.8 to 18.8 C (Gardner, 1981). At 52 (Experiment 1) or 56 days of age (Experiment 2), all broilers were individually weighed (preshrink weight), wingbanded, and placed in coops in such a manner that each coop contained a representative of each sex, diet, and KC1 treatment from two houses (12 birds/coop). The cooped broilers were held overnight (12 hr, 32.2 to 22.2 C, Experiment 1, and 16 hr, 29.4 to 11.1 C, Experiment 2) without feed or water, then individually weighed (postshrink weight) immediately prior to slaughter by exsanguination. Broilers were subscalded (60 C) for 45 sec and picked in a rotary drum picker. At evisceration, giblets were collected from broiler carcasses, identified, and saved for later inclusion with ground carcasses for compositional evaluation. The eviscerated shells were individually weighed (eviscerated weight) then chilled overnight in unagitated ice-slush (1 C). After chilling, carcasses were suspended by the legs and allowed to drain for 15 min prior to a final weight (postchill weight) evaluation. Percent shrink, percent water uptake, percent shell yield (shrink and water uptake effects eliminated), and percent ready-to-cook (RTC) yield based on postshrink weight (shrink effect eliminated but water uptake effect included), and percent RTC yield based on preshrink or
TABLE 1. Composition of low, medium, and high energy finisher diets fed to broilers in summer and winter (Experiments 1 and 2)" Dietary energy level (kcal ME/kg) Ingredients
2665 (low;I
3056 (med)
33 35 (high)
Yellow corn Soybean meal (49% protein) Animal fat Wheat shorts Ground limestone Dicalcium phosphate (18.5% Ca, 22 to 24% P) Iodized salt DL-Methionine Microingredient mixb
49.79 19.00
70.25 26.50
60.10 30.60 6.00
28.00 1.10 1.10
1.10 1.10
1.10 1.10
.40 .11 .50
.40 .15 .50
.40 .20 .50
Potassium chloride (KCI) diets were formulated by adding .75% KC1 to each of the diets. Supplied the following activities per kilogram of diet: vitamin A; 6600 IU; vitamin D 3 , 2200 ICU; menadione dimethylpyrimidionol bisulfite, 22 mg; riboflavin, 4.4 mg; pantothenic acid, 13.2 mg; niacin, 39.6 mg; choline chloride, 499.4 mg; vitamin B 1 2 , 22 Mg; ethoxyquin, .0125%; manganese, 60 mg; iron, 50 mg; copper, 6 mg; cobalt, .0198 mg; iodine, 1.1 mg; zinc, 35 mg.
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for the first 4 weeks. Feed and water were supplied ad libitum. After the brooding period, the shutters were maintained open to allow equilibration of house and environmental temperature. Within each house, each pen of 28-day-old broilers was supplied with a finisher diet containing either 2665, 3056, or 3335 kcal ME/kg of diet (Table 1). Broilers in two houses received these diets from 29 days to 52 days of age in Experiment 1 and 29 days to 56 days of age in Experiment 2. Broilers in the other two houses received these same diets except that .75% potassium chloride (KC1) was added to each diet for the last 5 days of each experiment. This level of KC1 was selected for study because previous work by Riley et al. (1976) had shown this level to be the lowest reproducibly effective level for obtaining a response. Experiment 1 was conducted in July and August while Experiment 2 was conducted in February and March. The average daily maximum and minimum temperatures during the July and August period at this research location were 32.8 and 22.1 C, respectively (Gardner, 1981). The average daily maximum ranged from 27.8 to 36.7 C and the minimum temperature ranged from 20.0 to 23.9 C (Gardner, 1981). In the February and March period the average daily maximum temperature was 21.2 and the average daily minimum was 6.3 C (Gardner, 1981). In this period, the average
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JANKY ET AL.
RESULTS AND DISCUSSION
Body weights of 52-day-old broilers, reared in summer (Experiment 1), and 56-day-old broilers, reared in winter (Experiment 2) (Table 2), were increased significantly as dietary energy level was increased. In both experiments, the body weight difference between the broilers fed the low and medium energy level diets was larger than the body weight difference between broilers fed the medium and high energy level diets. This indicated that the growth rates of broilers fed the two higher energy level diets were more similar to each other than to the growth rate observed for broilers fed the lowest energy level diet. This factor was reflected in shell yields where the effects of shrink and water uptake were removed and in carcass composition (Table 2). In both summer and winter the carcasses of broilers fed the two higher energy level diets had similar shell yields, which were significantly higher than the shell yield observed for carcasses from broilers fed the lowest energy level diet (Table 2). Similar values for ether extract (fat) of whole carcasses, including neck and giblets, from broilers reared in summer (Experiment 1) were observed for samples from broilers fed the two higher energy level diets and were signifi-
cantly higher than the value obtained for samples from broilers fed the lowest energy level diet (Table 2). Moisture values for these same samples were inversely related to ether extract (fat) and significantly increased with lower dietary energy levels (Table 2). Carcasses from broilers fed the two lower energy level diets in winter (Experiment 2) had similar and significantly lower ether extract (fat) values than those obtained for carcasses from broilers fed the highest energy level diet (Table 2). As in Experiment 1 (summer), moisture values of carcasses from broilers reared in winter (Experiment 2) were inversely related to ether extract (fat) values and increased significantly as dietary energy level was decreased (Table 2). Protein and ash values of carcasses from broilers reared in summer or winter (Experiments 1 and 2) were not significantly affected by energy level of the diet fed (Table 2). In Experiment 1 (summer) water uptake during chilling was significantly higher for carcasses from broilers fed the lowest energy level diet when compared to carcasses from broilers fed the higher energy level diets (Table 2). As a result of this increase, ready-to-cook (RTC) carcass yield based on the postshrink weight of carcasses from broilers fed the lowest energy level diet, which was elevated,differed significantly from the postshrink RTC yield of carcasses from broilers fed the high energy level diet (Table 2). The RTC posthsrink-based yield did not differ significantly between carcasses from broilers fed the medium and high or low energy level diets (Table 2). In Experiment 2 (winter), energy level of the diet fed to broilers had no significant effect on carcass water uptake during chilling (Table 2). Thus, the relationship of dietary energy level to RTC postshrink yield (Table 2) was the same as had been observed for percent shell yield. The higher energy level diets produced broilers with a significantly better postshrink RTC yield than did the lowest energy level diet. Because the smaller carcass would have a larger surface area per unit of mass than the larger carcass due to a lower mass/volume ratio, it would be expected that the smaller carcass would absorb more water than the larger carcass on a percentage of weight basis. This was statistically the case in Experiment 1 (summer) but only numerically true in Experiment 2 (winter).
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live weight (shrink and water uptake effects included) were calculated using the formulae shown in Table 2. Five male and five female carcasses were randomly selected from each pen and ground, with the respective cleaned giblets, by sex, through a .95-cm plate. These composites were then mixed thoroughly by hand and ground through a .31-cm plate. Triplicate samples of each composite were analyzed for percent moisture, percent protein, percent ether extract (fat), and percent ash using standard methods of Association of Official Analytical Chemists (AOAC, 1970). Within each experiment, all data were analyzed using the general linear model (GLM) for analysis of variance (Steel and Torrie, 1960) program available in the Statistical Analysis System (Helwig and Council, 1979). Because neither house nor sex interacted significantly with diet or KCl level, data from the two houses and sexes were combined. There were no significant interactions between diet and KCl level; therefore, only main effects were presented and discussed.
6
5
4
3
2
1735b 64.30b 14.1lb 67.23 b 16.65a 2.84a 5.13a 67.60ab 4.88 b 64.31 a
3056 (med) 1836c 64.68b 14.50b 66.23 a 16.48a 2.9ia 5.22a 68.06b 5.56c 64.27a
3335 (high) 2077a 64.8 13.0 66.7 17.6 2.8 5.4 68.3 6.8 63.7
2665 (
% RTC yield = (postchill weight/preshrink weight) X 100.
% Shrink = (preshrink weight — postshrink weight/preshrink weight) X 100.
% RTC yield = (postchill weight/postshrink weight) X 100.
% Water uptake = (postchill weight — eviscerated weight/eviscerated weight) X 100.
% Shell yield = (eviscerated weight/postshrink weight) X 100.
Body weight at 52 days of age (summer) and 56 days of age (winter).
' ' Means within a parameter and season followed by different superscripts are significantly different (P<.05).
1556* 63.47a 12.0ia 69.68 c 16.70a 2.86 a 5.79 b 67.13a 4.35a 64.2ia
Body weight1 Shell yield 2 , % Ether extract, % Moisture, % Protein, % Ash, % Water uptake, 3 % RTC yield, (postshrink wt), 4 % Shrink,5 % RTC yield (preshrink wt), 6 %
1
2665 (low)
Parameter
Dietary energy level (kcal ME/kg)
Summer (Jul —Aug)
TABLE 2. Body weights, carcass composition (with neck and giblets), shrink, water uptake and ready-to-c without neck and giblets from broilers fed low, medium, or high energy diets in summer (Experimen
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2002
JANKY ET AL. environmental temperature could be explained by differences in body size. Under cool conditions (winter), the smaller broiler with its larger surface area as compared to body weight would utilize more energy per gram of body weight in maintaining body heat than would a larger broiler. During the shrink period, with feed unavailable, this would logically result in more weight loss and, thus, a higher percent shrink in the smaller broiler. During warm weather shrink periods, the smaller broiler would have the advantage with a larger surface area per unit of mass for radiant heat dissipation. The larger bird must depend more on evaporative cooling through the respiratory tract as described by Ota et al. (1953). This was further confirmed by Reece et al. (1972) who indicated that mortality of large broilers (>1900 g) due to high temperature stress (40.6 C, 6 hr) was four times greater than that suffered by smaller broilers (< 1900 g). The present data indicated that feeding low energy diets in summer would not affect resulting carcass yield of broilers due to a more favorable percent shrink. However, feeding low energy diets in winter would tend to decrease carcass yield due to a less favorable percent shrink of the live broiler. The addition of .75% KC1 to the diet available to summer-reared broilers (Experiment 1) significantly reduced 52-day body weight (Table 3). Body weights of winter reared
TABLE 3. Body weights, carcass composition (with neck and giblets), shrink, water uptake, and ready-to-cook (RTC) yield values for carcasses without neck and giblets from broilers fed diets containing either 0 or .75% potassium chloride (KCl) 5 days preslaughter in summer (Experiment 1) or winter (Experiment 2) Summer (Jul --Aug)
Winter (Feb - M a r )
Parameter
0% KCl
.75% KCl
0% KCl
.75% KCl
Body weight,1 g Shell yield,2 g Water upake, 2 % RTC yield (postshrink wt), 2 % Ether extract, % Moisture, % Protein, % Ash, % Shrink,2 % RTC yield (preshrink weight), 2 %
1737b 63.98 a 5.45 a 67.46 a 13.89 a 67.42 a 16.60 a 2.83 a 5.17 b 63.96 a
1669 a 64.28 a 5.35 a 67.71 a 13.19 a 68.01 a 16.63 a 2.91 a 4.64 a 64.65 b
2232 a 65.99 a 5.29 a 68.74 a 13.69 a 65.70 a 17.76 a 2.85 a 6.66 a 64.16 a
2189 a 65.22 a 5.46 a 68.78 a 13.81 a 65.85 a 17.52 a 2.84 a 6.65 a 64.21 a
ab ' Means within a parameter and season followed by different superscripts are significantly different (P<.05). 1
Body weight at 52 (summer) and 56 days of age (winter).
2
See Table 2.
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Shrink of live bird weight prior to slaughter was found to increase significantly with increased levels of energy in the diet of summerreared (Experiment 1) broilers (Table 2). The decreased shrink in the weight of smaller broilers (low energy diet) caused the RTC yield based on preshrink or live in-house weight to increase to a level comparable to the RTC preshrink yield observed for larger broilers fed medium or high energy diets. The data indicated no significant difference in RTC yield based on preshrink weight between carcasses from broilers fed the three dietary energy levels (Table 2). These findings contradict shrink and yield data reported by Janky et al. (1976). These authors found a numerically increased shrink with low dietary energy levels and a correspondingly significantly decreased RTC yield based on preshrink weight. In Experiment 2 (winter), however, these previously published findings were confirmed. Shrink was observed to be significantly higher for broilers fed the lowest energy level diet than for broilers fed either of the higher energy level diets (Table 2). As a result, the RTC yield based on preshrink body weight was significantly lower for carcasses from broilers fed the lowest energy level diet when compared to yield values of carcasses from broilers fed the highest energy level diets (Table 2). These contradictory findings associated with
BROILER YIELDS: POTASSIUM CHLORIDE, ENERGY, OR SEASON AC KNOWLEDGMENT
The studies reported herein were supported in part by a grant-in-aid from the International Minerals and Chemical Corporation, Mundelein, IL 60060.
REFERENCES Association of Official Analytical Chemists, 1970. Official methods of analysis. 11th ed. Washington, DC. Gardner, F. P., 1981. 1981 Seven year climatological data for Gainesville, Florida—location 2WSW, Agronomy farm. Agron. Agric. Res. Rep. AY8204. Helwig, J. T., and K. A. Council, 1979. SAS User's Guide. 1979 ed. SAS Inst., Inc. Raleigh, NC. Janky, D. M., P. K. Riley, and R. H. Harms, 1976. The effect of dietary energy level on dressing percentage of broilers. Poultry Sci. 55:2388— 2390. Ota, H., H. L. Garver, and W. Ashby, 1953. Heat and moisture production of laying hens. Agric. Eng. 34:163-167. Reece, F. N„ J. W. Deaton, and L. F. Kubena, 1972. Effects of high temperature and humidity on heat prostration of broiler chickens. Poultry Sci. 51:2021-2025. Riley, P. K., D. M. Janky, R. H. Harms, and J. L. Fry, 1976. The effect of dietary potassium chloride on broiler yields. Poultry Sci. 55:1505— 1507. Steel, R.G.D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill, New York, NY.
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56-day-old broilers, however, were not significantly affected by the addition of KCl to the diet (Table 3). Feeding KCl to market age broilers, regardless of season, tended to produce a diarrhea-like condition in these birds, which could be responsible for the significant body weight reduction in summer (Experiment 1) and the numerical reduction observed in Experiment 2 (winter). Shell yield, water uptake, and RTC yield based on postshrink body weight of broiler carcasses were not significantly affected by KCl addition to the diet of summer-reared (Table 3) or winter-reared (Table 3) broilers. In addition, the composition of the carcass was not affected by feeding KCl to the broiler in either experiment (Table 3). The addition of KCl to the broiler diet significantly reduced shrink and, correspondingly, increased RTC yield based on live in-house weight in Experiment 1 (summer) (Table 3) but had no effect on these parameters in Experiment 2 (winter) (Table 3). These data confirmed a hypothesis by Riley et al. (1976) that the addition of KCl to the broiler diet was beneficial to RTC yield only when relatively high environmental temperatures were encountered. This appeared to be true, regardless of body size, because there was no significant interaction between KCl dietary addition and dietary energy level of the diet.
2003
1983 Poultry Science 62:1998-2003 INTRODUCTION
It has long been recognized that environmental factors, especially temperature, have an effect on broiler production, mainly through decreased efficiency and increased costs. Due to escalating energy costs, the use of environmentally controlled housing in the Southeast may not solve these decreased efficiency problems within practical costs. In the Southeast, the temperature problem of most severity would appear to be excessive heat rather than excessive cold. Severe heat may cause heat prostration, death, or inefficient growth, especially in unacclimated broilers (Reece et al., 1972). The effects of heat on broilers could be more subtle, such as decreasing yields through excessive shrink due to evapotranspiration during preslaughter holding. Previous studies have indicated that energy level of the diet (Janky et al, 1976) and the addition of an electrolyte such as potassium chloride (KC1) (Riley et al, 1976) have an effect on ready-to-cook broiler yields. In these studies, numerical trends in ready-to-cook yields were observed that indicated an environ-
1
Florida Agricultural Experiment Stations Journal Series No. 4123.
mental interaction with dietary energy level, or electrolyte administration, or both. The purpose of these experiments was to clarify the relationship of dietary energy level and KC1 supplementation to broiler yields, shrink, and water uptake as affected by environmental temperature. EXPERIMENTAL PROCEDURE
In each of two experiments, 20 (10 male, 10 female) day-old Cobb color-sexed broilers were assigned to each of three pens (2.3 m ' ) contained in four experimental houses. The four houses were identical and were equipped with shuttered east and west windows. The four experimental houses are small (9.2 m 2 ) and located in an east-west line 32 m apart. All houses are subjected to the same amount of sun, wind, and other environmental conditions. In previous experiments in these houses, there have been no housing or housing x treatment effects on body weights or feed efficiencies. Due to these factors, each pen in each house was assumed to provide an identical environment to the other pens within the house and to the pens located in the other three houses. Broilers were fed a standard starter diet and reared on peanut-hull litter using a continuous lighting regimen supplemented with thermostatically-controlled infrared brooding lamps
1998
Downloaded from http://ps.oxfordjournals.org/ at toledo hospital on May 4, 2015
ABSTRACT Equal numbers of male and female Cobb color-sexed broilers (28 days of age) were fed finisher diets containing 2665, 3056, or 3 335 kcal ME/kg of diet. One-half of the birds on each dietary energy treatment were fed .75% potassium chloride (KC1) the last 5 days prior to slaughter. The experiments were conducted in winter (Feb to Mar) and in summer (Jul to Aug). Birds were processed and various yield parameters calculated. Raw ready-to-cook carcass composition was also determined. During winter, decreasing dietary energy level significantly decreased percent yield due to increased shrink. The addition of KC1 to the diet in winter had no effect on yield characteristics and composition was affected only slightly by KG treatment. In summer, percent shrink was significantly decreased as dietary energy level was decreased, whereas water uptake was significantly increased. This resulted in no dietary energy effect on ready-to-cook yield. Adding KC1 to the diet in summer increased ready-to-cook yield by decreasing shrink. Fat was increased as dietary energy level was increased in both summer and winter. Moisture was inversely related to fat. (Key words.- energy, yields, broiler, seasonal variation, potassium chloride)
BROILER YIELDS: POTASSIUM CHLORIDE, ENERGY, OR SEASON
daily maximum ranged from 10.0 to 28.9 C and the average daily minimum ranged from —2.8 to 18.8 C (Gardner, 1981). At 52 (Experiment 1) or 56 days of age (Experiment 2), all broilers were individually weighed (preshrink weight), wingbanded, and placed in coops in such a manner that each coop contained a representative of each sex, diet, and KC1 treatment from two houses (12 birds/coop). The cooped broilers were held overnight (12 hr, 32.2 to 22.2 C, Experiment 1, and 16 hr, 29.4 to 11.1 C, Experiment 2) without feed or water, then individually weighed (postshrink weight) immediately prior to slaughter by exsanguination. Broilers were subscalded (60 C) for 45 sec and picked in a rotary drum picker. At evisceration, giblets were collected from broiler carcasses, identified, and saved for later inclusion with ground carcasses for compositional evaluation. The eviscerated shells were individually weighed (eviscerated weight) then chilled overnight in unagitated ice-slush (1 C). After chilling, carcasses were suspended by the legs and allowed to drain for 15 min prior to a final weight (postchill weight) evaluation. Percent shrink, percent water uptake, percent shell yield (shrink and water uptake effects eliminated), and percent ready-to-cook (RTC) yield based on postshrink weight (shrink effect eliminated but water uptake effect included), and percent RTC yield based on preshrink or
TABLE 1. Composition of low, medium, and high energy finisher diets fed to broilers in summer and winter (Experiments 1 and 2)" Dietary energy level (kcal ME/kg) Ingredients
2665 (low;I
3056 (med)
33 35 (high)
Yellow corn Soybean meal (49% protein) Animal fat Wheat shorts Ground limestone Dicalcium phosphate (18.5% Ca, 22 to 24% P) Iodized salt DL-Methionine Microingredient mixb
49.79 19.00
70.25 26.50
60.10 30.60 6.00
28.00 1.10 1.10
1.10 1.10
1.10 1.10
.40 .11 .50
.40 .15 .50
.40 .20 .50
Potassium chloride (KCI) diets were formulated by adding .75% KC1 to each of the diets. Supplied the following activities per kilogram of diet: vitamin A; 6600 IU; vitamin D 3 , 2200 ICU; menadione dimethylpyrimidionol bisulfite, 22 mg; riboflavin, 4.4 mg; pantothenic acid, 13.2 mg; niacin, 39.6 mg; choline chloride, 499.4 mg; vitamin B 1 2 , 22 Mg; ethoxyquin, .0125%; manganese, 60 mg; iron, 50 mg; copper, 6 mg; cobalt, .0198 mg; iodine, 1.1 mg; zinc, 35 mg.
Downloaded from http://ps.oxfordjournals.org/ at toledo hospital on May 4, 2015
for the first 4 weeks. Feed and water were supplied ad libitum. After the brooding period, the shutters were maintained open to allow equilibration of house and environmental temperature. Within each house, each pen of 28-day-old broilers was supplied with a finisher diet containing either 2665, 3056, or 3335 kcal ME/kg of diet (Table 1). Broilers in two houses received these diets from 29 days to 52 days of age in Experiment 1 and 29 days to 56 days of age in Experiment 2. Broilers in the other two houses received these same diets except that .75% potassium chloride (KC1) was added to each diet for the last 5 days of each experiment. This level of KC1 was selected for study because previous work by Riley et al. (1976) had shown this level to be the lowest reproducibly effective level for obtaining a response. Experiment 1 was conducted in July and August while Experiment 2 was conducted in February and March. The average daily maximum and minimum temperatures during the July and August period at this research location were 32.8 and 22.1 C, respectively (Gardner, 1981). The average daily maximum ranged from 27.8 to 36.7 C and the minimum temperature ranged from 20.0 to 23.9 C (Gardner, 1981). In the February and March period the average daily maximum temperature was 21.2 and the average daily minimum was 6.3 C (Gardner, 1981). In this period, the average
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JANKY ET AL.
RESULTS AND DISCUSSION
Body weights of 52-day-old broilers, reared in summer (Experiment 1), and 56-day-old broilers, reared in winter (Experiment 2) (Table 2), were increased significantly as dietary energy level was increased. In both experiments, the body weight difference between the broilers fed the low and medium energy level diets was larger than the body weight difference between broilers fed the medium and high energy level diets. This indicated that the growth rates of broilers fed the two higher energy level diets were more similar to each other than to the growth rate observed for broilers fed the lowest energy level diet. This factor was reflected in shell yields where the effects of shrink and water uptake were removed and in carcass composition (Table 2). In both summer and winter the carcasses of broilers fed the two higher energy level diets had similar shell yields, which were significantly higher than the shell yield observed for carcasses from broilers fed the lowest energy level diet (Table 2). Similar values for ether extract (fat) of whole carcasses, including neck and giblets, from broilers reared in summer (Experiment 1) were observed for samples from broilers fed the two higher energy level diets and were signifi-
cantly higher than the value obtained for samples from broilers fed the lowest energy level diet (Table 2). Moisture values for these same samples were inversely related to ether extract (fat) and significantly increased with lower dietary energy levels (Table 2). Carcasses from broilers fed the two lower energy level diets in winter (Experiment 2) had similar and significantly lower ether extract (fat) values than those obtained for carcasses from broilers fed the highest energy level diet (Table 2). As in Experiment 1 (summer), moisture values of carcasses from broilers reared in winter (Experiment 2) were inversely related to ether extract (fat) values and increased significantly as dietary energy level was decreased (Table 2). Protein and ash values of carcasses from broilers reared in summer or winter (Experiments 1 and 2) were not significantly affected by energy level of the diet fed (Table 2). In Experiment 1 (summer) water uptake during chilling was significantly higher for carcasses from broilers fed the lowest energy level diet when compared to carcasses from broilers fed the higher energy level diets (Table 2). As a result of this increase, ready-to-cook (RTC) carcass yield based on the postshrink weight of carcasses from broilers fed the lowest energy level diet, which was elevated,differed significantly from the postshrink RTC yield of carcasses from broilers fed the high energy level diet (Table 2). The RTC posthsrink-based yield did not differ significantly between carcasses from broilers fed the medium and high or low energy level diets (Table 2). In Experiment 2 (winter), energy level of the diet fed to broilers had no significant effect on carcass water uptake during chilling (Table 2). Thus, the relationship of dietary energy level to RTC postshrink yield (Table 2) was the same as had been observed for percent shell yield. The higher energy level diets produced broilers with a significantly better postshrink RTC yield than did the lowest energy level diet. Because the smaller carcass would have a larger surface area per unit of mass than the larger carcass due to a lower mass/volume ratio, it would be expected that the smaller carcass would absorb more water than the larger carcass on a percentage of weight basis. This was statistically the case in Experiment 1 (summer) but only numerically true in Experiment 2 (winter).
Downloaded from http://ps.oxfordjournals.org/ at toledo hospital on May 4, 2015
live weight (shrink and water uptake effects included) were calculated using the formulae shown in Table 2. Five male and five female carcasses were randomly selected from each pen and ground, with the respective cleaned giblets, by sex, through a .95-cm plate. These composites were then mixed thoroughly by hand and ground through a .31-cm plate. Triplicate samples of each composite were analyzed for percent moisture, percent protein, percent ether extract (fat), and percent ash using standard methods of Association of Official Analytical Chemists (AOAC, 1970). Within each experiment, all data were analyzed using the general linear model (GLM) for analysis of variance (Steel and Torrie, 1960) program available in the Statistical Analysis System (Helwig and Council, 1979). Because neither house nor sex interacted significantly with diet or KCl level, data from the two houses and sexes were combined. There were no significant interactions between diet and KCl level; therefore, only main effects were presented and discussed.
6
5
4
3
2
1735b 64.30b 14.1lb 67.23 b 16.65a 2.84a 5.13a 67.60ab 4.88 b 64.31 a
3056 (med) 1836c 64.68b 14.50b 66.23 a 16.48a 2.9ia 5.22a 68.06b 5.56c 64.27a
3335 (high) 2077a 64.8 13.0 66.7 17.6 2.8 5.4 68.3 6.8 63.7
2665 (
% RTC yield = (postchill weight/preshrink weight) X 100.
% Shrink = (preshrink weight — postshrink weight/preshrink weight) X 100.
% RTC yield = (postchill weight/postshrink weight) X 100.
% Water uptake = (postchill weight — eviscerated weight/eviscerated weight) X 100.
% Shell yield = (eviscerated weight/postshrink weight) X 100.
Body weight at 52 days of age (summer) and 56 days of age (winter).
' ' Means within a parameter and season followed by different superscripts are significantly different (P<.05).
1556* 63.47a 12.0ia 69.68 c 16.70a 2.86 a 5.79 b 67.13a 4.35a 64.2ia
Body weight1 Shell yield 2 , % Ether extract, % Moisture, % Protein, % Ash, % Water uptake, 3 % RTC yield, (postshrink wt), 4 % Shrink,5 % RTC yield (preshrink wt), 6 %
1
2665 (low)
Parameter
Dietary energy level (kcal ME/kg)
Summer (Jul —Aug)
TABLE 2. Body weights, carcass composition (with neck and giblets), shrink, water uptake and ready-to-c without neck and giblets from broilers fed low, medium, or high energy diets in summer (Experimen
oaded from http://ps.oxfordjournals.org/ at toledo hospital on May 4, 2015
2002
JANKY ET AL. environmental temperature could be explained by differences in body size. Under cool conditions (winter), the smaller broiler with its larger surface area as compared to body weight would utilize more energy per gram of body weight in maintaining body heat than would a larger broiler. During the shrink period, with feed unavailable, this would logically result in more weight loss and, thus, a higher percent shrink in the smaller broiler. During warm weather shrink periods, the smaller broiler would have the advantage with a larger surface area per unit of mass for radiant heat dissipation. The larger bird must depend more on evaporative cooling through the respiratory tract as described by Ota et al. (1953). This was further confirmed by Reece et al. (1972) who indicated that mortality of large broilers (>1900 g) due to high temperature stress (40.6 C, 6 hr) was four times greater than that suffered by smaller broilers (< 1900 g). The present data indicated that feeding low energy diets in summer would not affect resulting carcass yield of broilers due to a more favorable percent shrink. However, feeding low energy diets in winter would tend to decrease carcass yield due to a less favorable percent shrink of the live broiler. The addition of .75% KC1 to the diet available to summer-reared broilers (Experiment 1) significantly reduced 52-day body weight (Table 3). Body weights of winter reared
TABLE 3. Body weights, carcass composition (with neck and giblets), shrink, water uptake, and ready-to-cook (RTC) yield values for carcasses without neck and giblets from broilers fed diets containing either 0 or .75% potassium chloride (KCl) 5 days preslaughter in summer (Experiment 1) or winter (Experiment 2) Summer (Jul --Aug)
Winter (Feb - M a r )
Parameter
0% KCl
.75% KCl
0% KCl
.75% KCl
Body weight,1 g Shell yield,2 g Water upake, 2 % RTC yield (postshrink wt), 2 % Ether extract, % Moisture, % Protein, % Ash, % Shrink,2 % RTC yield (preshrink weight), 2 %
1737b 63.98 a 5.45 a 67.46 a 13.89 a 67.42 a 16.60 a 2.83 a 5.17 b 63.96 a
1669 a 64.28 a 5.35 a 67.71 a 13.19 a 68.01 a 16.63 a 2.91 a 4.64 a 64.65 b
2232 a 65.99 a 5.29 a 68.74 a 13.69 a 65.70 a 17.76 a 2.85 a 6.66 a 64.16 a
2189 a 65.22 a 5.46 a 68.78 a 13.81 a 65.85 a 17.52 a 2.84 a 6.65 a 64.21 a
ab ' Means within a parameter and season followed by different superscripts are significantly different (P<.05). 1
Body weight at 52 (summer) and 56 days of age (winter).
2
See Table 2.
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Shrink of live bird weight prior to slaughter was found to increase significantly with increased levels of energy in the diet of summerreared (Experiment 1) broilers (Table 2). The decreased shrink in the weight of smaller broilers (low energy diet) caused the RTC yield based on preshrink or live in-house weight to increase to a level comparable to the RTC preshrink yield observed for larger broilers fed medium or high energy diets. The data indicated no significant difference in RTC yield based on preshrink weight between carcasses from broilers fed the three dietary energy levels (Table 2). These findings contradict shrink and yield data reported by Janky et al. (1976). These authors found a numerically increased shrink with low dietary energy levels and a correspondingly significantly decreased RTC yield based on preshrink weight. In Experiment 2 (winter), however, these previously published findings were confirmed. Shrink was observed to be significantly higher for broilers fed the lowest energy level diet than for broilers fed either of the higher energy level diets (Table 2). As a result, the RTC yield based on preshrink body weight was significantly lower for carcasses from broilers fed the lowest energy level diet when compared to yield values of carcasses from broilers fed the highest energy level diets (Table 2). These contradictory findings associated with
BROILER YIELDS: POTASSIUM CHLORIDE, ENERGY, OR SEASON AC KNOWLEDGMENT
The studies reported herein were supported in part by a grant-in-aid from the International Minerals and Chemical Corporation, Mundelein, IL 60060.
REFERENCES Association of Official Analytical Chemists, 1970. Official methods of analysis. 11th ed. Washington, DC. Gardner, F. P., 1981. 1981 Seven year climatological data for Gainesville, Florida—location 2WSW, Agronomy farm. Agron. Agric. Res. Rep. AY8204. Helwig, J. T., and K. A. Council, 1979. SAS User's Guide. 1979 ed. SAS Inst., Inc. Raleigh, NC. Janky, D. M., P. K. Riley, and R. H. Harms, 1976. The effect of dietary energy level on dressing percentage of broilers. Poultry Sci. 55:2388— 2390. Ota, H., H. L. Garver, and W. Ashby, 1953. Heat and moisture production of laying hens. Agric. Eng. 34:163-167. Reece, F. N„ J. W. Deaton, and L. F. Kubena, 1972. Effects of high temperature and humidity on heat prostration of broiler chickens. Poultry Sci. 51:2021-2025. Riley, P. K., D. M. Janky, R. H. Harms, and J. L. Fry, 1976. The effect of dietary potassium chloride on broiler yields. Poultry Sci. 55:1505— 1507. Steel, R.G.D., and J. H. Torrie, 1960. Principles and Procedures of Statistics. McGraw-Hill, New York, NY.
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56-day-old broilers, however, were not significantly affected by the addition of KCl to the diet (Table 3). Feeding KCl to market age broilers, regardless of season, tended to produce a diarrhea-like condition in these birds, which could be responsible for the significant body weight reduction in summer (Experiment 1) and the numerical reduction observed in Experiment 2 (winter). Shell yield, water uptake, and RTC yield based on postshrink body weight of broiler carcasses were not significantly affected by KCl addition to the diet of summer-reared (Table 3) or winter-reared (Table 3) broilers. In addition, the composition of the carcass was not affected by feeding KCl to the broiler in either experiment (Table 3). The addition of KCl to the broiler diet significantly reduced shrink and, correspondingly, increased RTC yield based on live in-house weight in Experiment 1 (summer) (Table 3) but had no effect on these parameters in Experiment 2 (winter) (Table 3). These data confirmed a hypothesis by Riley et al. (1976) that the addition of KCl to the broiler diet was beneficial to RTC yield only when relatively high environmental temperatures were encountered. This appeared to be true, regardless of body size, because there was no significant interaction between KCl dietary addition and dietary energy level of the diet.
2003