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Effect of the Age of Chickens on the True Metabolizable Energy Values of Feed Ingredients1
Effect of the Age of Chickens on the True Metabolizable Energy Values of Feed Ingredients1 A. SHIRES 2 , A. R. ROBBLEE, R. T. HARDIN, and D. R. CLANDININ Department of Animal Science, University of Alberta, Edmonton, Alberta T6G 2E3, Canada (Received for publication December 9, 1977) ABSTRACT White Leghorn male 4-week-old chicks and adult roosters were used to determine the effect of age on the true metabolizable energy (TME) and nitrogen-corrected true metabolizable energy (TME,,) value of ground yellow corn, dehulled soybean meal, wheat shorts, high-glucosinolate rapeseed meal, and dehydrated alfalfa meal. The TME and TME n values of each ingredient were calculated from its gross energy value and the regression of energy voided as excreta on the weight of feed consumed. Variable intakes of corn and soybean meal were obtained with chicks by feeding different amounts of the feedstuffs and with roosters by varying the duration of the feeding period. Variable intakes of the other ingredients were obtained by the force feeding of the birds. The TME values of the feedstuffs in kcal/g of dry matter for chicks and roosters, respectively, were as follows: corn, 3.93 and 3.98; soybean meal, 3.24 and 3.11; wheat shorts, 3.12 and 3.07; rapeseed meal, 2.24 and 2.50; alfalfa meal, 1.22 and 1.38. The TME n values of the feedstuffs for chicks and roosters, respectively, were as follows: corn, 3.76 and 3.88; soybean meal, 2.85 and 2.87; wheat shorts, 2.92 and 2.94; rapeseed meal, 1.99 and 2.24;alfalfa meal, 1.14 and 1.28. The TME values of soybean meal and rapeseed meal for chicks were 104% (P<.05) and 90% (P<.05), respectively, of the values obtained with roosters. The TME n values of corn and rapeseed meal for chicks were 97% (P<.05) and 89% (P<.01), respectively, of the values for roosters. The TME and TME n values of the other feedstuffs were not affected (P>.05) by the age of the bird. It appears that, with the exception of high-glucosinolate rapeseed meal, TME values obtained with adult roosters can be used in the formulation of diets for young growing birds. 1980 Poultry Science 59:396-403
INTRODUCTION Metabolizable energy is t h e difference b e t w e e n gross energy of t h e feed eaten and gross energy of t h e excreta ( N R C , 1 9 6 6 ) . T h e d e t e r m i n a t i o n of m e t a b o l i z a b l e energy b y conventional m e t h o d s is laborious and expensive. T h e assays yield a p p a r e n t m e t a b o l i z a b l e energy (AME) values which m a y be corrected for nitrogen retained or lost from t h e b o d y ( A M E n ) . T h e AME values of feedstuffs have b e e n s h o w n t o vary with t h e age (Bayley et al, 1 9 6 8 ; Zelenka, 1 9 6 8 ; L o d h i et al, 1 9 6 9 ) , strain and breed (Sibbald and Slinger, 1 9 6 3 ; Slinger et al., 1 9 6 4 ; Foster, 1 9 6 8 ) , and species (Slinger et al, 1 9 6 4 ; Bayley et al, 1 9 6 8 ; Fisher and S h a n n o n , 1 9 7 3 ; Leeson et al, 1974) of t h e assay bird and with t h e level of feed intake
1 This study was presented at the 28th Annual Meeting of the Canadian Society of Animal Science, Regina, Saskatchewan, July 2 to 6, 1978. 2 Present address: Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan S7N 0W0, Canada.
(Sibbald, 1 9 7 5 ) . T h e curvilinear relationship b e t w e e n feed intake and AME value reported b y Sibbald ( 1 9 7 5 ) m a y be explained b y the observation t h a t u n d e r standardized conditions t h e e x c r e t i o n of m e t a b o l i c fecal energy ( F E m ) and endoge n o u s u r i n a r y energy ( U E e ) is c o n s t a n t (Guillaume and S u m m e r s , 1 9 7 0 ) . At high levels of feed i n t a k e t h e F E m + U E e losses are small relative t o t h e excretion of energy of feed origin and have o n l y a m i n o r influence o n t h e AME value. At l o w levels of feed i n t a k e t h e F E m + U E e losses are p r o p o r t i o n a t e l y large and result in a decrease in t h e AME value. Sibbald ( 1 9 7 5 ) suggested t h a t s o m e of t h e differences in AME values associated with age, strain, and species m a y be a t t r i b u t a b l e t o variations in t h e F E m + U E e losses relative t o t h e excreta energy losses of feed origin. If this is correct, t h e n t h e d e t e r m i n a t i o n of t r u e m e t a bolizable energy (TME) should provide a m o r e reliable estimate of t h e available energy c o n t e n t of a feedstuff t h a n conventional assays for A M E . T h e calculation of t h e TME value o f a feedstuff involves t h e correction of t h e gross
396
EFFECT OF AGE ON TRUE ME
energy of the excreta for F E m + UE e losses (NRC, 1966). A bioassay for TME was developed recently by Sibbald (1976a) which is relatively simple and rapid. Studies with adult birds indicated that the TME value of a feedstuff was independent of feed intake (Sibbald, 1975,1976a) and, with the exception of soybean meal, was not affected by the strain or species of the assay bird (Sibbald, 1976b). Since the assay developed by Sibbald (1976a) to determine the TME value of a feedstuff uses adult roosters, which are considered to be in nitrogen equilibrium, it is important to determine if the values can be applied to the formulation of diets for young growing birds. The work described in this report was designed to investigate the effect of the age of the chicken on the TME and nitrogen-corrected true metabolizable energy (TME n ) values of five feed ingredients selected to vary widely in available energy content. MATERIALS AND METHODS
Experimental Animals. Single Comb White Leghorn (Shaver Starcross 288) male chickens were used in the experiments. Chicks were reared in an electrically heated, thermostatically controlled battery brooder with wire screen floors in a temperature controlled room. At 2 weeks of age chicks were wingbanded and transferred to individual cages. Five bioassays for TME were conducted at 4 weeks of age, with a single feedstuff and 45 to 60 chicks per assay. Roosters, 16 to 24 months of age, were housed in individual cages in a windowless room. Alternate cages were left vacant to minimize the possibility of cross contamination of excreta. Five bioassays were conducted at intervals of 2 weeks or longer with a single feedstuff and 36 roosters per assay. Between assays, feed and water were supplied ad libitum. The composition of the diet fed to chicks and roosters is shown in Table 1. Room lighting was controlled automatically to provide 12 hr of light and 12 hr of darkness. Bioassay of Feedstuffs. The procedure of Sibbald (1975, 1976a) was used to determine the TME value of ground yellow corn, dehulled soybean meal, wheat shorts, rapeseed meal, and dehydrated alfalfa meal. The nitrogen and gross energy contents of the feedstuffs in g/100 g and kcal/g of dry matter, respectively, were as follows: corn, 1.57 and 4.46; soybean meal, 8.58 and 4.74; wheat shorts, 2.92 and 4.62; rapeseed meal, 6.44 and 4.80; alfalfa meal,
397
TABLE 1. Composition of diet for chicks and roosters Ingredient
%
Yellow corn, ground Wheat, ground Soybean meal (49% protein) Fish meal (67% protein) Alfalfa meal (17% protein) Whey, dried Soybean oil Limestone, ground Dicalcium phosphate* Vitamin mix 2 Salt, iodized Mineral mix 3 Chemical composition Protein (analyzed), % AME n (calculated), kcal/g
32.5 32.5 20.0 5.0 2.5 2.0 2.0 1.5 1.2 .4 .3 .1 21.6 3.07
Dicalcium phosphate contained 18.5% Ca and 20.5% P. 2 Vitamin mix supplied the following per kilogram of diet: vitamin A, 8000 IU; vitamin D 3 , 1000 ICU; vitamin E, 10 IU; menadione sodium bisulfite, 1 mg; riboflavin, 4 mg; d-calcium pantothenate, 10 mg; niacin, 20 mg; choline chloride, 500 mg; folic acid, 1 mg; vitamin B 1 2 , 10 /zg; pyridoxine HCl, 3 mg; d-biotin, 200 Mgi thiamin HCl, 1 mg; DL-methionine, 500 mg; ethoxyquin, 125 mg. Mineral mix supplied the following in mg/kg of diet: manganese, 100 (MnO); zinc, 100 (ZnO); iron, 50 ( F e S 0 4 - 7 H 2 0 ) ; copper, 5 ( C u S 0 4 - 5 H 2 0 ) ; iodine, 1 (KIO a ); selenium, .1 (Na 2 Se0 3 ).
2.87 and 4.39. The rapeseed meal was produced from seed low in erucic acid and had a potential oxazolidinethione and isothiocyanate content of 6.3 and 2.5 mg/g, respectively. Prior to each assay, chicks and roosters were starved for 21 hr and then weighed individually. Chicks with body weights nearest to the mean were selected and allocated to groups of three birds. The allocation of birds to groups was made on the basis of body weight, to equalize both mean body weight and body weight distribution among groups. The groups of birds were assigned at random to provide two or three replicates at each level of feed intake. Variable intakes of corn and soybean meal were obtained with chicks by feeding different amounts (0 to 16 g/bird) of the feedstuff in increments of 2 g for a period of 8 hr. The residual feed was weighed. The individual intakes of rapeseed meal (0 to 12 g), alfalfa meal (0 to 10 g), and wheat shorts (0 to 8 g) were increased by increments of 2 g and were varied by force feeding the chicks a half portion
SHIRES ETAL.
398
of the feedstuff twice. Force feeding was completed within a period of 6 to 8 hr. Twentyfour hours after the start of the assay, the chicks were weighed again. The excreta voided by each group of birds during the 24-hr period were combined and collected quantitatively. Palpation of the crop at the termination of an assay occasionally revealed the presence of feed. The data obtained from these birds were discarded. Excreta were collected from 88 groups of chicks in the five assays. Variable intakes of corn (0 to 84 g/bird) and soybean meal (0 to 59 g/bird) were obtained with roosters by varying the duration of the feeding period. Roosters were given 500 g of corn or soybean meal and the feed containers were removed at intervals ranging from .25 to 8 hr. The residual feed was weighed. The individual intakes of rapeseed meal (0 to 36 g), alfalfa meal (0 to 36 g), and wheat shorts (0 to 25 g) were increased by increments of 6, 6, and 5 g, respectively, and were varied by force feeding the roosters a single sample of the feedstuff. Twenty-four hours after the start of the experiment the birds were weighed again and the excreta voided by each bird during the previous 24 hr were collected quantitatively. Excreta were collected from 178 roosters in the five assays. The excreta were frozen, freeze-dried, allowed to come to equilibrium with atmospheric moisture, weighed, and finely ground. Samples of the excreta and feedstuffs were assayed for gross energy by bomb calorimetry and for nitrogen and moisture by the methods described by the AOAC (1970). The data were expressed on a dry matter (DM) basis. A value of 8.22 kcal/g of nitrogen was used to correct the gross energy of the excreta for nitrogen retained or lost from the body (Hill and Anderson, 1958). Statistical Analysis. The relationships between feed intake and gross energy voided as excreta by groups of three chicks and single roosters were established by regression analysis. The regression coefficients established for each feedstuff by young and adult birds were tested for homogeneity by analysis of covariance (Steel and Torrie, I960).
RESULTS AND DISCUSSION
A linear relationship between feed intake and gross energy of excreta was established for each feedstuff with groups of three chicks and
single roosters. The regression equations are presented in Table 2, where the value of Y represents gross energy of excreta in kcal and the value of X represents feed intake in grams of dry matter. The correlation coefficients (r) for all feedstuffs at each age were highly significant (P<.01). The data are in agreement with the reports of Sibbald (1975, 1976a) which were based solely on assays with adult roosters. The regression coefficients (b) established for each feedstuff with chicks and roosters were tested for homogeneity, and the results of the t-test are given in Table 2. It was found that for soybean meal and rapeseed meal the slopes of the regression lines were significantly (P<.05) affected by the age of the bird. The effect of correction of excreta energy for nitrogen retained or lost from the body on the regression lines is presented in Table 3. It was observed that correction to nitrogen equilibrium reduced the variation about the regression lines and increased the magnitude of the regression coefficients particularly for chicks. The correlation coefficients for all feedstuffs at each age were highly significant (P<.01). The difference between the regression coefficients in response to age was nonsignificant (P>.05) for soybean meal, wheat shorts, and alfalfa meal and significant for corn (P<.05) and rapeseed meal (P<.01). The effect of age and correction to nitrogen equilibrium on the energy values of the feedstuffs is illustrated more clearly by expression of the data in terms of TME and TME n values and by calculation of the chick:adult ratio of these values for each feedstuff. The results of these calculations are shown in Table 4. The TME and TME n values of each feedstuff for chicks and roosters were calculated by subtraction of the appropriate regression coefficient from the gross energy value of the feedstuff. It was demonstrated that the TME n values of corn and rapeseed meal for chicks were 97% (P<.05) and 89% (P<.01), respectively, of the values for roosters. Petersen et al. (1976) reported that the AME n value of corn for chicks was 90% of the value obtained with laying hens. In contrast, Hochstetler and Scott (1975) observed that the AME n value of corn was not affected by the age of the bird. It appears that the age of the bird has little or no effect on the TME n or AME n value of corn. The data for rapeseed meal are in agreement with previous studies of the effect of age on the AME n value of this ingredient. It has been
399
EFFECT OF AGE ON TRUE ME TABLE 2. Regression ofkcal of gross energy voided as excreta (Y) on g of feed intake (X) for groups of three chicks and single roosters* Adult
Chick Feedstuff
Y = a + bX
*b
Corn meal Soybean meal Wheat shorts Rapeseed meal Alfalfa meal
14.32+ 15.11 + 15.38+ 15.28+ 15.86+
.036 .027 .057 .034 .081
.531X 1.503X 1.494X 2.558X 3.176X
2
r3
df+
Y = a + bX
%
r
df
t-value^
.961**
18 18 13 14 15
10.54+ 12.98+ 10.53+ 11.72+ 9.38 +
.026 .038 .079 .065 .101
.954** .991** .958** .987** .983**
34 34 34 34 32
-
Q07**
.991** .999** .995**
.482X 1.626X 1.553X 2.300X 3.016X
.91 2.12* .44 -2.51* - .91
Values are expressed on a dry matter basis. 2 Standard error of the regression coefficient. Correlation coefficient. Degrees of freedom for error. Test for homogeneity of regression coefficients between ages. »P<.05. **P<.01.
pentosans than rapeseed meal, were not affected (P>.05) by the age of the bird (Table 3 and 4). The data indicate that other factors present in rapeseed meal, such as tannins (Yapar and Clandinin, 1972) and thiogiucosides (Lodhi et al, 1970), may have a greater influence on the TME n value of rapeseed meal for chicks than pentosans. It appeared from the data presented in Table 4 that chicks utilized 11 to 12% less of the total energy in alfalfa meal than roosters. However, the differences between the regression coefficients were nonsignificant (Table 2 and 3) and
reported that the AME n value of high-glucosinolate rapeseed meal for young chicks was 67% (Lodhi et al, 1969) and 61% (March et al, 1973) of the value obtained with laying hens. March et al. (1973) suggested that the high pentosan content of rapeseed meal (Clandinin and Rao, 1970) may account for some of the differences between ages in the AME n value of rapeseed meal, since Bolton (1955) reported that the digestibility of pentosans increases with the age of the bird. It was noted, however, that the TME n values of wheat shorts and alfalfa meal, which contain higher levels of
TABLE 3. Regression ofkcal of gross energy voided as excreta and corrected to nitrogen equilibrium (Y) on g of feed intake (X) for groups of three chicks and single roosters^
Feedstuff
Y = a + bX
Corn meal Soybean meal Wheat shorts Rapeseed meal Alfalfa meal
6.77+ 6.91 + 6.41+ 6.72+ 5.60+
.703X 1.887X 1.700X 2.815X 3.247X
Chick sb2 .029 .024 .044 .027 .073
Adult r3
df4
Y = abX
.985** .999** .996** .999** .996**
18 18 13 14 15
5.63 + 7.82 + 5.25 + 6.42 + 4.04+
Values are expressed on a dry matter basis. Standard error of the regression coefficient. Correlation coefficient. Degrees of freedom for error. Test for homogeneity of regression coefficients between ages. *P<.05. **P<.01.
.578X 1.868X 1.678X 2.559X 3.114X
% .025 .035 .082 .055 .093
r
t-value^
df .969** 994** .962** .992** .986**
34 34 34 34 32
-2.46* - .36 - .16 -2.99** - .83
400
SHIRES ET AL.
TABLE 4. True metabolizable energy (TMB) and nitrogen-corrected true metabolizable energy (TMEn) values of feedstuffs for chicks and adult roosters and a comparison of the ratios of these values with ratios of nitrogen-corrected apparent metabolizable energy (AMEn) values reported in the literature for chicks and laying hens or roosters kcal/g of Dry matter TME 1
TMEn 1
Ratio of chick: adult values
Feedstuff
Chick
Adult
Chick
Adult
TME
TME n
AME n
Corn meal Soybean meal Wheat shorts Rapeseed meal Alfalfa meal
3.93 3.24 3.12 2.24 1.22
3.98 3.11 3.07 2.50 1.38
3.76 2.85 2.92 1.99 1.14
3.88 2.87 2.94 2.24 1.28
.99 1.04 1.02 .90 .88
.97 .99 .99 .89 .89
.90 2 .632 .863 .674 .54 2
Calculated by subtraction of the regression coefficient from the gross energy of the feedstuff. Petersen et al. (1976). 3 Bayley«a/. (1968). 4 Lodhi«a/. (1969). were largely the result of two values obtained with roosters force fed 22 and 28 g of alfalfa meal (DM basis), which deviated grossly from the regression line (Figure 1). The omission of the inconsistent values from the data of roosters resulted in a TME value of 1.25 kcal/g and a TME n value of 1.16 kcal/g for alfalfa meal (DM basis). The chick:adult ratios of the TME and TME n values for alfalfa meal were .98 and .99, respectively. The correction to nitrogen equilibrium resulted in reductions of 2 to 12% in the energy value of the feedstuffs, but with two exceptions, corn and soybean meal, had no significant effect on the chick:adult ratio of the values. The chick:adult ratio of the TME and TME n values for corn were .99 and .97, and for soybean meal were 1.04 and .99, respectively. The changes in the energy values of corn and soybean meal in response to nitrogen correction were significant (P<.05). A linear relationship between grams of nitrogen consumed (X) and excreted (Y) by groups of three chicks and single roosters was established (P<.01) for each feedstuff except wheat shorts (P>.05), which exhibited no relationship between these variables for chicks (Table 5). The difference between the regression coefficients associated with age was significant for corn (P<.001), soybean meal (P<.001), and wheat shorts (P<.05) but was nonsignificant for the other feedstuffs. The greatest effect of age on nitrogen excretion resulted from the consumption of corn at levels below the maintenance require-
ment for energy (Figure 2). The regression coefficients for chicks and roosters fed corn meal were —.33 and +.26, respectively. The differential response of chicks and roosters to
120
C\J
100
chick
o
y = 5.60 + r-
3.247X
.996
adult • y = 4.04 + 3. 114 X f-
20
ALFALFA FIG. 1. Relationship gross energy voided as nitrogen equilibrium for single roosters.
.986
30
40
INTAKE , g DM between alfalfa intake and excreta and corrected to groups of three chicks and
EFFECT OF AGE ON TRUE ME
401
TABLE 5. Regression of g of nitrogen excreted (Y) on g of nitrogen consumed (X) by groups of three chicks and single roosters Chick Feedstuff
Y = a + bX
Corn meal Soybean meal Wheat shorts Rapeseed meal Alfalfa meal
.918 .998 1.092 1.042 1.248
Adult r2
Sb 1
- .330X + .45 5X + .140X + .515X +.698X
.081 .019 .072 .036 .096
-.693** .985** .472 .968** .883**
df
3
18 18 13 14 15
Y = a4 bX .599 + .627 + .643 + .645 + .649 +
.258X .657X .482X .510X .585X
s
b
.051 .014 .077 .034 .062
r
df
t-value^
.658** .992** .733** .933** .857**
34 34 34 34 32
5.40*** 8.33*** 2.56* - .08 - .94
Standard error of the regression coefficient. Correlation coefficient. Degrees of freedom for error Test for homogeneity of regression coefficients between ages. *P<.05. **P<.01. ***P<.001.
low intakes of corn may be explained in relation to the low protein and high starch content of corn and to the sparing effect of carbohydrate on protein degradation (Munro, 1951). Chicks contain less body fat than mature birds and, therefore, they are more dependent on body protein to provide energy and glucose via gluconeogenesis for the maintenance of vital body functions during a period of deprivation than adult birds. The digestion of starch provides glucose, and its utilization serves to spare the catabolism of labile protein reserves and muscle. The response line of chicks may be expected to curve upwards at higher intakes of corn as more corn protein is degraded and the nitrogenous products excreted, although there was no evidence for this trend within the narrow range of intakes observed in this study
.0
8
• • .8
.6
---"''
> o 0
•• • •• •
• _•..-•- -°>^~~~-~,
• * > - ' '
••
• chick
o
y = .918 - .330X r - -.693
adult
•
y - .599 + .258 X T • .658
.4
CORN
NITROGEN
INTAKE , g
FIG. 2. Relationship between corn nitrogen intake and nitrogen excretion by groups of three chicks and single roosters.
(Figure 2). The relative importance of protein degradation to maintain the vital body functions of chicks and adult birds during a fast is evident from an analysis of the losses in body weight and nitrogen. A total of 54 chicks and 53 roosters received no feed during the assay periods. At the start of the assays, mean body weight (± SD) of the unfed chicks and roosters were 273 ± 27 g and 2782 ± 204 g, respectively. The unfed chicks and roosters suffered a mean body weight loss of 23.9 ± 2.9 g and 66 ± 15 g, respectively, during the 24-hr assay periods, which represent 8.8 and 2.4% of the initial body weights. It should be noted that the total weight loss of the birds was greater than the values reported, since all birds were subjected to an additional fast of 21 hr prior to the start of each assay. It was observed that the unfed chicks and roosters excreted on average 1313 ± 114 mg and 241 ± 48 mg of nitrogen/kg of body weight/24 hr, respectively. Since the regression coefficients obtained with chicks and roosters were heterogeneous, the five estimates (a) of the excreta energy output (Table 2), nitrogen-corrected energy output (Table 3), and nitrogen losses (Table 5) of chicks and roosters given no feed were tested for homogeneity by analysis of covariance. It was found that, with the exception of the estimates of nitrogen losses by unfed chicks, the differences between the predicted values were nonsignificant. The predicted value of 1.248 g of nitrogen obtained by the force feeding of alfalfa meal was significantly
402
SHIRES ETAL.
(P<.05) greater than the other four estimates of nitrogen output by unfed chicks (Table 5). No significant differences were found between the observed values of energy or nitrogen output by unfed chicks and roosters. The observation that the force feeding of alfalfa meal was associated with a significantly greater estimate of nitrogen loss by unfed chicks may be explained in terms of the effect of dietary fiber on the excretion of metabolic fecal nitrogen. The crude fiber content of dehydrated alfalfa meal (17% protein) is about 24%, which is 2 to 12 times greater than the crude fiber content of the other feedstuffs. Whiting and Bezeau (1957) reported that the excretion of metabolic fecal nitrogen was directly related to the amount of fiber in the diet. Sibbald (1975) suggested that the differences in AME associated with age, strain, and species may be attributable in part to variations in the FE m + UE e losses relative to the output of energy of feed origin. If this is true, then the correction of AME for F E m + UE e losses may provide a more reliable estimate of the available energy value of feedstuffs. A comparison was made, therefore, of the ratios of TME n values with appropriate ratios of AMEn values reported in the literature for chicks and laying hens (Lodhi et al, 1969; Petersen et al, 1976) or roosters (Bayley et al, 1968) and the results are presented in Table 4. It was noted that the age of the bird had a much greater influence on the AME n values as compared to the TME n values. This observation may be explained by the correction of excreta energy for FE m + UE e losses (Sibbald, 1975) or by the more efficient utilization of fibrous materials by chicks at low levels of feed intake. The results of this study provide no evidence that the relationship between feed intake and gross energy of excreta was nonlinear at the highest levels of intake (Figure 1). It may be concluded that the correction of AME for F E m + UE e losses decreases the variation attributable to the age of the bird and that, with the exception of high-glucosinolate rapeseed meal, TME values obtained with adult roosters are applicable to the formulation of diets for young growing birds.
ACKNOWLEDGMENTS This work was supported in part by grants from the National Research Council of Canada, the Alberta Agricultural Research Trust, and
the Rapeseed Association of Canada. The technical assistance of B. Fougere-Tower is gratefully acknowledged. The authors wish to thank Y. K. Goh for analysis of glucosinolates in rapeseed meal. REFERENCES Association of Official Analytical Chemists, 1970. Official methods of analysis. 11th ed. AOAC, Washington, DC. Bayley, H. S., J. D. Summers, and S. J. Slinger, 1968. Effect of heat-treatment on the metabolizable energy value of wheat germ meal and other wheat milling by-products. Cereal Chem. 45:557—563. Bolton, W., 1955. The digestibility of the carbohydrate complex by birds of different ages. J. Agr. Sci. 46:420-424. Clandinin, D. R., and P. V. Rao, 1970. Pentosans in prepress-solvent and solvent processed rapeseed meal. Poultry Sci. 49:1741-1742. Fisher, C , and D. W. F. Shannon, 1973. Metabolisable energy determinations using chicks and turkeys. Brit. Poultry Sci. 14:609-613. Foster, W. H., 1968. Variation between and within birds in the estimation of the metabolizable energy content of diets for laying hens. J. Agr. Sci. 71:153-159. Guillaume, J., and J. D. Summers, 1970. Maintenance energy requirement of the rooster and influence of plane of nutrition on metabolizable energy. Can. J. Anim. Sci. 50:363-369. Hill, F. W., and D. L. Anderson, 1958. Comparison of metabolizable energy and productive energy determinations with growing chicks. J. Nutr. 64:587-603. Hochstetler, H. W., and M. L. Scott, 1975. Metabolizable energy determinations with adult chickens. Pages 81—86 in Proc. Cornell Nutr. Conf. Leeson, S., K. N. Boorman, D. Lewis, and D. H. Shrimpton, 1974. Metabolisable energy studies with turkeys: metabolisable energy of dietary ingredients. Brit. Poultry Sci. 15:183-189. Lodhi, G. N., D. R. Clandinin, and R. Renner, 1970. Factors affecting the metabolizable energy value of rapeseed meal. 1. Goitrogens. Poultry Sci. 49:289-294. Lodhi, G. N., R. Renner, and D. R. Clandinin, 1969. Studies on the metabolizable energy of rapeseed meal for growing chickens and laying hens. Poultry Sci. 48:964-970. March, B. E., T. Smith, and S. El-Lakany, 1973. Variation in estimates of the metabolizable energy value of rapeseed meal determined with chickens of different ages. Poultry Sci. 52:614— 618. Munro, H. N., 1951. Carbohydrate and fat as factors in protein utilization and metabolism. Physiol Rev. 31:449-488. National Research Council, 1966. Biological energy interrelationships and glossary of energy terms. 2nd ed. Nat. Acad. Sci., Washington, DC. Petersen, C. F., G. B. Meyer, and E.A. Sauter, 1976. Comparison of metabolizable energy values of feed ingredients for chicks and hens. Poultry Sci. 55:1163-1165.
EFFECT OF AGE ON TRUE ME Sibbald, I. R., 1975. The effect of level of feed intake on metabolizable energy values measured with adult roosters. Poultry Sci. 54:1990-1997. Sibbald, I. R., 1976a. A bioassay for true metabolizable energy in feedingstuffs. Poultry Sci. 55:303-308. Sibbald, I. R., 1976b. The true metabolizable energy values of several feedingstuffs measured with roosters, laying hens, turkeys and broiler hens. Poultry Sci. 55:1459-1463. Sibbald, I. R., and S. J. Slinger, 1963. The effects of breed, sex, an arsenical and nutrient density on the utilization of dietary energy. Poultry Sci. 42:1325-1332. Slinger, S. J., I. R. Sibbald, and W. F. Pepper, 1964. The relative abilities of two breeds of chickens
403
and two varieties of turkeys to metabolize dietary energy and dietary nitrogen. Poultry Sci. 43:329-333. Steel, R. G. D., and J. H. Torrie, 1960. Principles and procedures of statistics. McGraw-Hill Book Co., Inc., New York, NY. Whiting, F., and L. M. Bezeau, 1957. The metabolic fecal nitrogen excretion of the pig as influenced by the amount of fiber in the ration and by body weight. Can. J. Anim. Sci. 37:95-105. Yapar, Z., and D. R. Clandinin, 1972. Effect of tannins in rapeseed meal on its nutritional value for chicks. Poultry Sci. 51:222-228. Zelenka, J., 1968. Influence of the age of chicken on the metabolisable energy values of poultry diets. Brit. Poultry Sci. 9-135-142.
INTRODUCTION Metabolizable energy is t h e difference b e t w e e n gross energy of t h e feed eaten and gross energy of t h e excreta ( N R C , 1 9 6 6 ) . T h e d e t e r m i n a t i o n of m e t a b o l i z a b l e energy b y conventional m e t h o d s is laborious and expensive. T h e assays yield a p p a r e n t m e t a b o l i z a b l e energy (AME) values which m a y be corrected for nitrogen retained or lost from t h e b o d y ( A M E n ) . T h e AME values of feedstuffs have b e e n s h o w n t o vary with t h e age (Bayley et al, 1 9 6 8 ; Zelenka, 1 9 6 8 ; L o d h i et al, 1 9 6 9 ) , strain and breed (Sibbald and Slinger, 1 9 6 3 ; Slinger et al., 1 9 6 4 ; Foster, 1 9 6 8 ) , and species (Slinger et al, 1 9 6 4 ; Bayley et al, 1 9 6 8 ; Fisher and S h a n n o n , 1 9 7 3 ; Leeson et al, 1974) of t h e assay bird and with t h e level of feed intake
1 This study was presented at the 28th Annual Meeting of the Canadian Society of Animal Science, Regina, Saskatchewan, July 2 to 6, 1978. 2 Present address: Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan S7N 0W0, Canada.
(Sibbald, 1 9 7 5 ) . T h e curvilinear relationship b e t w e e n feed intake and AME value reported b y Sibbald ( 1 9 7 5 ) m a y be explained b y the observation t h a t u n d e r standardized conditions t h e e x c r e t i o n of m e t a b o l i c fecal energy ( F E m ) and endoge n o u s u r i n a r y energy ( U E e ) is c o n s t a n t (Guillaume and S u m m e r s , 1 9 7 0 ) . At high levels of feed i n t a k e t h e F E m + U E e losses are small relative t o t h e excretion of energy of feed origin and have o n l y a m i n o r influence o n t h e AME value. At l o w levels of feed i n t a k e t h e F E m + U E e losses are p r o p o r t i o n a t e l y large and result in a decrease in t h e AME value. Sibbald ( 1 9 7 5 ) suggested t h a t s o m e of t h e differences in AME values associated with age, strain, and species m a y be a t t r i b u t a b l e t o variations in t h e F E m + U E e losses relative t o t h e excreta energy losses of feed origin. If this is correct, t h e n t h e d e t e r m i n a t i o n of t r u e m e t a bolizable energy (TME) should provide a m o r e reliable estimate of t h e available energy c o n t e n t of a feedstuff t h a n conventional assays for A M E . T h e calculation of t h e TME value o f a feedstuff involves t h e correction of t h e gross
396
EFFECT OF AGE ON TRUE ME
energy of the excreta for F E m + UE e losses (NRC, 1966). A bioassay for TME was developed recently by Sibbald (1976a) which is relatively simple and rapid. Studies with adult birds indicated that the TME value of a feedstuff was independent of feed intake (Sibbald, 1975,1976a) and, with the exception of soybean meal, was not affected by the strain or species of the assay bird (Sibbald, 1976b). Since the assay developed by Sibbald (1976a) to determine the TME value of a feedstuff uses adult roosters, which are considered to be in nitrogen equilibrium, it is important to determine if the values can be applied to the formulation of diets for young growing birds. The work described in this report was designed to investigate the effect of the age of the chicken on the TME and nitrogen-corrected true metabolizable energy (TME n ) values of five feed ingredients selected to vary widely in available energy content. MATERIALS AND METHODS
Experimental Animals. Single Comb White Leghorn (Shaver Starcross 288) male chickens were used in the experiments. Chicks were reared in an electrically heated, thermostatically controlled battery brooder with wire screen floors in a temperature controlled room. At 2 weeks of age chicks were wingbanded and transferred to individual cages. Five bioassays for TME were conducted at 4 weeks of age, with a single feedstuff and 45 to 60 chicks per assay. Roosters, 16 to 24 months of age, were housed in individual cages in a windowless room. Alternate cages were left vacant to minimize the possibility of cross contamination of excreta. Five bioassays were conducted at intervals of 2 weeks or longer with a single feedstuff and 36 roosters per assay. Between assays, feed and water were supplied ad libitum. The composition of the diet fed to chicks and roosters is shown in Table 1. Room lighting was controlled automatically to provide 12 hr of light and 12 hr of darkness. Bioassay of Feedstuffs. The procedure of Sibbald (1975, 1976a) was used to determine the TME value of ground yellow corn, dehulled soybean meal, wheat shorts, rapeseed meal, and dehydrated alfalfa meal. The nitrogen and gross energy contents of the feedstuffs in g/100 g and kcal/g of dry matter, respectively, were as follows: corn, 1.57 and 4.46; soybean meal, 8.58 and 4.74; wheat shorts, 2.92 and 4.62; rapeseed meal, 6.44 and 4.80; alfalfa meal,
397
TABLE 1. Composition of diet for chicks and roosters Ingredient
%
Yellow corn, ground Wheat, ground Soybean meal (49% protein) Fish meal (67% protein) Alfalfa meal (17% protein) Whey, dried Soybean oil Limestone, ground Dicalcium phosphate* Vitamin mix 2 Salt, iodized Mineral mix 3 Chemical composition Protein (analyzed), % AME n (calculated), kcal/g
32.5 32.5 20.0 5.0 2.5 2.0 2.0 1.5 1.2 .4 .3 .1 21.6 3.07
Dicalcium phosphate contained 18.5% Ca and 20.5% P. 2 Vitamin mix supplied the following per kilogram of diet: vitamin A, 8000 IU; vitamin D 3 , 1000 ICU; vitamin E, 10 IU; menadione sodium bisulfite, 1 mg; riboflavin, 4 mg; d-calcium pantothenate, 10 mg; niacin, 20 mg; choline chloride, 500 mg; folic acid, 1 mg; vitamin B 1 2 , 10 /zg; pyridoxine HCl, 3 mg; d-biotin, 200 Mgi thiamin HCl, 1 mg; DL-methionine, 500 mg; ethoxyquin, 125 mg. Mineral mix supplied the following in mg/kg of diet: manganese, 100 (MnO); zinc, 100 (ZnO); iron, 50 ( F e S 0 4 - 7 H 2 0 ) ; copper, 5 ( C u S 0 4 - 5 H 2 0 ) ; iodine, 1 (KIO a ); selenium, .1 (Na 2 Se0 3 ).
2.87 and 4.39. The rapeseed meal was produced from seed low in erucic acid and had a potential oxazolidinethione and isothiocyanate content of 6.3 and 2.5 mg/g, respectively. Prior to each assay, chicks and roosters were starved for 21 hr and then weighed individually. Chicks with body weights nearest to the mean were selected and allocated to groups of three birds. The allocation of birds to groups was made on the basis of body weight, to equalize both mean body weight and body weight distribution among groups. The groups of birds were assigned at random to provide two or three replicates at each level of feed intake. Variable intakes of corn and soybean meal were obtained with chicks by feeding different amounts (0 to 16 g/bird) of the feedstuff in increments of 2 g for a period of 8 hr. The residual feed was weighed. The individual intakes of rapeseed meal (0 to 12 g), alfalfa meal (0 to 10 g), and wheat shorts (0 to 8 g) were increased by increments of 2 g and were varied by force feeding the chicks a half portion
SHIRES ETAL.
398
of the feedstuff twice. Force feeding was completed within a period of 6 to 8 hr. Twentyfour hours after the start of the assay, the chicks were weighed again. The excreta voided by each group of birds during the 24-hr period were combined and collected quantitatively. Palpation of the crop at the termination of an assay occasionally revealed the presence of feed. The data obtained from these birds were discarded. Excreta were collected from 88 groups of chicks in the five assays. Variable intakes of corn (0 to 84 g/bird) and soybean meal (0 to 59 g/bird) were obtained with roosters by varying the duration of the feeding period. Roosters were given 500 g of corn or soybean meal and the feed containers were removed at intervals ranging from .25 to 8 hr. The residual feed was weighed. The individual intakes of rapeseed meal (0 to 36 g), alfalfa meal (0 to 36 g), and wheat shorts (0 to 25 g) were increased by increments of 6, 6, and 5 g, respectively, and were varied by force feeding the roosters a single sample of the feedstuff. Twenty-four hours after the start of the experiment the birds were weighed again and the excreta voided by each bird during the previous 24 hr were collected quantitatively. Excreta were collected from 178 roosters in the five assays. The excreta were frozen, freeze-dried, allowed to come to equilibrium with atmospheric moisture, weighed, and finely ground. Samples of the excreta and feedstuffs were assayed for gross energy by bomb calorimetry and for nitrogen and moisture by the methods described by the AOAC (1970). The data were expressed on a dry matter (DM) basis. A value of 8.22 kcal/g of nitrogen was used to correct the gross energy of the excreta for nitrogen retained or lost from the body (Hill and Anderson, 1958). Statistical Analysis. The relationships between feed intake and gross energy voided as excreta by groups of three chicks and single roosters were established by regression analysis. The regression coefficients established for each feedstuff by young and adult birds were tested for homogeneity by analysis of covariance (Steel and Torrie, I960).
RESULTS AND DISCUSSION
A linear relationship between feed intake and gross energy of excreta was established for each feedstuff with groups of three chicks and
single roosters. The regression equations are presented in Table 2, where the value of Y represents gross energy of excreta in kcal and the value of X represents feed intake in grams of dry matter. The correlation coefficients (r) for all feedstuffs at each age were highly significant (P<.01). The data are in agreement with the reports of Sibbald (1975, 1976a) which were based solely on assays with adult roosters. The regression coefficients (b) established for each feedstuff with chicks and roosters were tested for homogeneity, and the results of the t-test are given in Table 2. It was found that for soybean meal and rapeseed meal the slopes of the regression lines were significantly (P<.05) affected by the age of the bird. The effect of correction of excreta energy for nitrogen retained or lost from the body on the regression lines is presented in Table 3. It was observed that correction to nitrogen equilibrium reduced the variation about the regression lines and increased the magnitude of the regression coefficients particularly for chicks. The correlation coefficients for all feedstuffs at each age were highly significant (P<.01). The difference between the regression coefficients in response to age was nonsignificant (P>.05) for soybean meal, wheat shorts, and alfalfa meal and significant for corn (P<.05) and rapeseed meal (P<.01). The effect of age and correction to nitrogen equilibrium on the energy values of the feedstuffs is illustrated more clearly by expression of the data in terms of TME and TME n values and by calculation of the chick:adult ratio of these values for each feedstuff. The results of these calculations are shown in Table 4. The TME and TME n values of each feedstuff for chicks and roosters were calculated by subtraction of the appropriate regression coefficient from the gross energy value of the feedstuff. It was demonstrated that the TME n values of corn and rapeseed meal for chicks were 97% (P<.05) and 89% (P<.01), respectively, of the values for roosters. Petersen et al. (1976) reported that the AME n value of corn for chicks was 90% of the value obtained with laying hens. In contrast, Hochstetler and Scott (1975) observed that the AME n value of corn was not affected by the age of the bird. It appears that the age of the bird has little or no effect on the TME n or AME n value of corn. The data for rapeseed meal are in agreement with previous studies of the effect of age on the AME n value of this ingredient. It has been
399
EFFECT OF AGE ON TRUE ME TABLE 2. Regression ofkcal of gross energy voided as excreta (Y) on g of feed intake (X) for groups of three chicks and single roosters* Adult
Chick Feedstuff
Y = a + bX
*b
Corn meal Soybean meal Wheat shorts Rapeseed meal Alfalfa meal
14.32+ 15.11 + 15.38+ 15.28+ 15.86+
.036 .027 .057 .034 .081
.531X 1.503X 1.494X 2.558X 3.176X
2
r3
df+
Y = a + bX
%
r
df
t-value^
.961**
18 18 13 14 15
10.54+ 12.98+ 10.53+ 11.72+ 9.38 +
.026 .038 .079 .065 .101
.954** .991** .958** .987** .983**
34 34 34 34 32
-
Q07**
.991** .999** .995**
.482X 1.626X 1.553X 2.300X 3.016X
.91 2.12* .44 -2.51* - .91
Values are expressed on a dry matter basis. 2 Standard error of the regression coefficient. Correlation coefficient. Degrees of freedom for error. Test for homogeneity of regression coefficients between ages. »P<.05. **P<.01.
pentosans than rapeseed meal, were not affected (P>.05) by the age of the bird (Table 3 and 4). The data indicate that other factors present in rapeseed meal, such as tannins (Yapar and Clandinin, 1972) and thiogiucosides (Lodhi et al, 1970), may have a greater influence on the TME n value of rapeseed meal for chicks than pentosans. It appeared from the data presented in Table 4 that chicks utilized 11 to 12% less of the total energy in alfalfa meal than roosters. However, the differences between the regression coefficients were nonsignificant (Table 2 and 3) and
reported that the AME n value of high-glucosinolate rapeseed meal for young chicks was 67% (Lodhi et al, 1969) and 61% (March et al, 1973) of the value obtained with laying hens. March et al. (1973) suggested that the high pentosan content of rapeseed meal (Clandinin and Rao, 1970) may account for some of the differences between ages in the AME n value of rapeseed meal, since Bolton (1955) reported that the digestibility of pentosans increases with the age of the bird. It was noted, however, that the TME n values of wheat shorts and alfalfa meal, which contain higher levels of
TABLE 3. Regression ofkcal of gross energy voided as excreta and corrected to nitrogen equilibrium (Y) on g of feed intake (X) for groups of three chicks and single roosters^
Feedstuff
Y = a + bX
Corn meal Soybean meal Wheat shorts Rapeseed meal Alfalfa meal
6.77+ 6.91 + 6.41+ 6.72+ 5.60+
.703X 1.887X 1.700X 2.815X 3.247X
Chick sb2 .029 .024 .044 .027 .073
Adult r3
df4
Y = abX
.985** .999** .996** .999** .996**
18 18 13 14 15
5.63 + 7.82 + 5.25 + 6.42 + 4.04+
Values are expressed on a dry matter basis. Standard error of the regression coefficient. Correlation coefficient. Degrees of freedom for error. Test for homogeneity of regression coefficients between ages. *P<.05. **P<.01.
.578X 1.868X 1.678X 2.559X 3.114X
% .025 .035 .082 .055 .093
r
t-value^
df .969** 994** .962** .992** .986**
34 34 34 34 32
-2.46* - .36 - .16 -2.99** - .83
400
SHIRES ET AL.
TABLE 4. True metabolizable energy (TMB) and nitrogen-corrected true metabolizable energy (TMEn) values of feedstuffs for chicks and adult roosters and a comparison of the ratios of these values with ratios of nitrogen-corrected apparent metabolizable energy (AMEn) values reported in the literature for chicks and laying hens or roosters kcal/g of Dry matter TME 1
TMEn 1
Ratio of chick: adult values
Feedstuff
Chick
Adult
Chick
Adult
TME
TME n
AME n
Corn meal Soybean meal Wheat shorts Rapeseed meal Alfalfa meal
3.93 3.24 3.12 2.24 1.22
3.98 3.11 3.07 2.50 1.38
3.76 2.85 2.92 1.99 1.14
3.88 2.87 2.94 2.24 1.28
.99 1.04 1.02 .90 .88
.97 .99 .99 .89 .89
.90 2 .632 .863 .674 .54 2
Calculated by subtraction of the regression coefficient from the gross energy of the feedstuff. Petersen et al. (1976). 3 Bayley«a/. (1968). 4 Lodhi«a/. (1969). were largely the result of two values obtained with roosters force fed 22 and 28 g of alfalfa meal (DM basis), which deviated grossly from the regression line (Figure 1). The omission of the inconsistent values from the data of roosters resulted in a TME value of 1.25 kcal/g and a TME n value of 1.16 kcal/g for alfalfa meal (DM basis). The chick:adult ratios of the TME and TME n values for alfalfa meal were .98 and .99, respectively. The correction to nitrogen equilibrium resulted in reductions of 2 to 12% in the energy value of the feedstuffs, but with two exceptions, corn and soybean meal, had no significant effect on the chick:adult ratio of the values. The chick:adult ratio of the TME and TME n values for corn were .99 and .97, and for soybean meal were 1.04 and .99, respectively. The changes in the energy values of corn and soybean meal in response to nitrogen correction were significant (P<.05). A linear relationship between grams of nitrogen consumed (X) and excreted (Y) by groups of three chicks and single roosters was established (P<.01) for each feedstuff except wheat shorts (P>.05), which exhibited no relationship between these variables for chicks (Table 5). The difference between the regression coefficients associated with age was significant for corn (P<.001), soybean meal (P<.001), and wheat shorts (P<.05) but was nonsignificant for the other feedstuffs. The greatest effect of age on nitrogen excretion resulted from the consumption of corn at levels below the maintenance require-
ment for energy (Figure 2). The regression coefficients for chicks and roosters fed corn meal were —.33 and +.26, respectively. The differential response of chicks and roosters to
120
C\J
100
chick
o
y = 5.60 + r-
3.247X
.996
adult • y = 4.04 + 3. 114 X f-
20
ALFALFA FIG. 1. Relationship gross energy voided as nitrogen equilibrium for single roosters.
.986
30
40
INTAKE , g DM between alfalfa intake and excreta and corrected to groups of three chicks and
EFFECT OF AGE ON TRUE ME
401
TABLE 5. Regression of g of nitrogen excreted (Y) on g of nitrogen consumed (X) by groups of three chicks and single roosters Chick Feedstuff
Y = a + bX
Corn meal Soybean meal Wheat shorts Rapeseed meal Alfalfa meal
.918 .998 1.092 1.042 1.248
Adult r2
Sb 1
- .330X + .45 5X + .140X + .515X +.698X
.081 .019 .072 .036 .096
-.693** .985** .472 .968** .883**
df
3
18 18 13 14 15
Y = a4 bX .599 + .627 + .643 + .645 + .649 +
.258X .657X .482X .510X .585X
s
b
.051 .014 .077 .034 .062
r
df
t-value^
.658** .992** .733** .933** .857**
34 34 34 34 32
5.40*** 8.33*** 2.56* - .08 - .94
Standard error of the regression coefficient. Correlation coefficient. Degrees of freedom for error Test for homogeneity of regression coefficients between ages. *P<.05. **P<.01. ***P<.001.
low intakes of corn may be explained in relation to the low protein and high starch content of corn and to the sparing effect of carbohydrate on protein degradation (Munro, 1951). Chicks contain less body fat than mature birds and, therefore, they are more dependent on body protein to provide energy and glucose via gluconeogenesis for the maintenance of vital body functions during a period of deprivation than adult birds. The digestion of starch provides glucose, and its utilization serves to spare the catabolism of labile protein reserves and muscle. The response line of chicks may be expected to curve upwards at higher intakes of corn as more corn protein is degraded and the nitrogenous products excreted, although there was no evidence for this trend within the narrow range of intakes observed in this study
.0
8
• • .8
.6
---"''
> o 0
•• • •• •
• _•..-•- -°>^~~~-~,
• * > - ' '
••
• chick
o
y = .918 - .330X r - -.693
adult
•
y - .599 + .258 X T • .658
.4
CORN
NITROGEN
INTAKE , g
FIG. 2. Relationship between corn nitrogen intake and nitrogen excretion by groups of three chicks and single roosters.
(Figure 2). The relative importance of protein degradation to maintain the vital body functions of chicks and adult birds during a fast is evident from an analysis of the losses in body weight and nitrogen. A total of 54 chicks and 53 roosters received no feed during the assay periods. At the start of the assays, mean body weight (± SD) of the unfed chicks and roosters were 273 ± 27 g and 2782 ± 204 g, respectively. The unfed chicks and roosters suffered a mean body weight loss of 23.9 ± 2.9 g and 66 ± 15 g, respectively, during the 24-hr assay periods, which represent 8.8 and 2.4% of the initial body weights. It should be noted that the total weight loss of the birds was greater than the values reported, since all birds were subjected to an additional fast of 21 hr prior to the start of each assay. It was observed that the unfed chicks and roosters excreted on average 1313 ± 114 mg and 241 ± 48 mg of nitrogen/kg of body weight/24 hr, respectively. Since the regression coefficients obtained with chicks and roosters were heterogeneous, the five estimates (a) of the excreta energy output (Table 2), nitrogen-corrected energy output (Table 3), and nitrogen losses (Table 5) of chicks and roosters given no feed were tested for homogeneity by analysis of covariance. It was found that, with the exception of the estimates of nitrogen losses by unfed chicks, the differences between the predicted values were nonsignificant. The predicted value of 1.248 g of nitrogen obtained by the force feeding of alfalfa meal was significantly
402
SHIRES ETAL.
(P<.05) greater than the other four estimates of nitrogen output by unfed chicks (Table 5). No significant differences were found between the observed values of energy or nitrogen output by unfed chicks and roosters. The observation that the force feeding of alfalfa meal was associated with a significantly greater estimate of nitrogen loss by unfed chicks may be explained in terms of the effect of dietary fiber on the excretion of metabolic fecal nitrogen. The crude fiber content of dehydrated alfalfa meal (17% protein) is about 24%, which is 2 to 12 times greater than the crude fiber content of the other feedstuffs. Whiting and Bezeau (1957) reported that the excretion of metabolic fecal nitrogen was directly related to the amount of fiber in the diet. Sibbald (1975) suggested that the differences in AME associated with age, strain, and species may be attributable in part to variations in the FE m + UE e losses relative to the output of energy of feed origin. If this is true, then the correction of AME for F E m + UE e losses may provide a more reliable estimate of the available energy value of feedstuffs. A comparison was made, therefore, of the ratios of TME n values with appropriate ratios of AMEn values reported in the literature for chicks and laying hens (Lodhi et al, 1969; Petersen et al, 1976) or roosters (Bayley et al, 1968) and the results are presented in Table 4. It was noted that the age of the bird had a much greater influence on the AME n values as compared to the TME n values. This observation may be explained by the correction of excreta energy for FE m + UE e losses (Sibbald, 1975) or by the more efficient utilization of fibrous materials by chicks at low levels of feed intake. The results of this study provide no evidence that the relationship between feed intake and gross energy of excreta was nonlinear at the highest levels of intake (Figure 1). It may be concluded that the correction of AME for F E m + UE e losses decreases the variation attributable to the age of the bird and that, with the exception of high-glucosinolate rapeseed meal, TME values obtained with adult roosters are applicable to the formulation of diets for young growing birds.
ACKNOWLEDGMENTS This work was supported in part by grants from the National Research Council of Canada, the Alberta Agricultural Research Trust, and
the Rapeseed Association of Canada. The technical assistance of B. Fougere-Tower is gratefully acknowledged. The authors wish to thank Y. K. Goh for analysis of glucosinolates in rapeseed meal. REFERENCES Association of Official Analytical Chemists, 1970. Official methods of analysis. 11th ed. AOAC, Washington, DC. Bayley, H. S., J. D. Summers, and S. J. Slinger, 1968. Effect of heat-treatment on the metabolizable energy value of wheat germ meal and other wheat milling by-products. Cereal Chem. 45:557—563. Bolton, W., 1955. The digestibility of the carbohydrate complex by birds of different ages. J. Agr. Sci. 46:420-424. Clandinin, D. R., and P. V. Rao, 1970. Pentosans in prepress-solvent and solvent processed rapeseed meal. Poultry Sci. 49:1741-1742. Fisher, C , and D. W. F. Shannon, 1973. Metabolisable energy determinations using chicks and turkeys. Brit. Poultry Sci. 14:609-613. Foster, W. H., 1968. Variation between and within birds in the estimation of the metabolizable energy content of diets for laying hens. J. Agr. Sci. 71:153-159. Guillaume, J., and J. D. Summers, 1970. Maintenance energy requirement of the rooster and influence of plane of nutrition on metabolizable energy. Can. J. Anim. Sci. 50:363-369. Hill, F. W., and D. L. Anderson, 1958. Comparison of metabolizable energy and productive energy determinations with growing chicks. J. Nutr. 64:587-603. Hochstetler, H. W., and M. L. Scott, 1975. Metabolizable energy determinations with adult chickens. Pages 81—86 in Proc. Cornell Nutr. Conf. Leeson, S., K. N. Boorman, D. Lewis, and D. H. Shrimpton, 1974. Metabolisable energy studies with turkeys: metabolisable energy of dietary ingredients. Brit. Poultry Sci. 15:183-189. Lodhi, G. N., D. R. Clandinin, and R. Renner, 1970. Factors affecting the metabolizable energy value of rapeseed meal. 1. Goitrogens. Poultry Sci. 49:289-294. Lodhi, G. N., R. Renner, and D. R. Clandinin, 1969. Studies on the metabolizable energy of rapeseed meal for growing chickens and laying hens. Poultry Sci. 48:964-970. March, B. E., T. Smith, and S. El-Lakany, 1973. Variation in estimates of the metabolizable energy value of rapeseed meal determined with chickens of different ages. Poultry Sci. 52:614— 618. Munro, H. N., 1951. Carbohydrate and fat as factors in protein utilization and metabolism. Physiol Rev. 31:449-488. National Research Council, 1966. Biological energy interrelationships and glossary of energy terms. 2nd ed. Nat. Acad. Sci., Washington, DC. Petersen, C. F., G. B. Meyer, and E.A. Sauter, 1976. Comparison of metabolizable energy values of feed ingredients for chicks and hens. Poultry Sci. 55:1163-1165.
EFFECT OF AGE ON TRUE ME Sibbald, I. R., 1975. The effect of level of feed intake on metabolizable energy values measured with adult roosters. Poultry Sci. 54:1990-1997. Sibbald, I. R., 1976a. A bioassay for true metabolizable energy in feedingstuffs. Poultry Sci. 55:303-308. Sibbald, I. R., 1976b. The true metabolizable energy values of several feedingstuffs measured with roosters, laying hens, turkeys and broiler hens. Poultry Sci. 55:1459-1463. Sibbald, I. R., and S. J. Slinger, 1963. The effects of breed, sex, an arsenical and nutrient density on the utilization of dietary energy. Poultry Sci. 42:1325-1332. Slinger, S. J., I. R. Sibbald, and W. F. Pepper, 1964. The relative abilities of two breeds of chickens
403
and two varieties of turkeys to metabolize dietary energy and dietary nitrogen. Poultry Sci. 43:329-333. Steel, R. G. D., and J. H. Torrie, 1960. Principles and procedures of statistics. McGraw-Hill Book Co., Inc., New York, NY. Whiting, F., and L. M. Bezeau, 1957. The metabolic fecal nitrogen excretion of the pig as influenced by the amount of fiber in the ration and by body weight. Can. J. Anim. Sci. 37:95-105. Yapar, Z., and D. R. Clandinin, 1972. Effect of tannins in rapeseed meal on its nutritional value for chicks. Poultry Sci. 51:222-228. Zelenka, J., 1968. Influence of the age of chicken on the metabolisable energy values of poultry diets. Brit. Poultry Sci. 9-135-142.