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Effect of the Previous Diet, Body Weight, and Duration of Starvation of the Assay Bird on the True Metabolizable Energy Value of Corn
Effect of the Previous Diet, Body Weight, and Duration of Starvation of the Assay Bird on the True Metabolizable Energy Value of Corn A. SHIRES 1 , A. R. ROBBLEE, R. T. HARDIN, and D. R. CLANDININ Department of Animal Science, The University of Alberta, Edmonton, Alberta T6G 2E3, Canada (Received for publication April 21, 1978)
1979 Poultry Science 58:602-608
INTRODUCTION
The bioassay developed by Sibbald (1976a) to measure the true metabolizable energy (TME) value of feedstuffs involves the force feeding of adult roosters with the material under test and the total collection of excreta. Prior to an assay, birds of similar body weight are paired and starved to empty their digestive tracts. After a fast of 21 hr, one member of each pair of birds is force fed a sample (ca. 25 g) of the feedstuff and the second member of the pair is starved. The excreta voided by each bird during the following period of 24 hr is collected quantitatively, dried, weighed, and analyzed for gross energy content. The TME value of the feedstuff is calculated as the difference between gross energy of the feed intake and gross energy of the excreta of the fed bird after correction of the latter for metabolic fecal energy ( F E m ) and endogenous urinary energy (UE e ). It is assumed that the excreta energy voided by the unfed bird provides a valid estimate of the F E m + UE e losses of the fed bird. The assay measures the TME value of a feedstuff when fed singly at
levels of intake below the maintenance requirement for energy. It is possible that the previous intake of protein and energy and the duration of the period of starvation prior to force feeding may influence the estimates of TME. Fritz et al. (1936) reported that the quantity of nitrogen excreted daily by adult roosters during a fast was related initially to the previous intake of protein until, on the third day of fasting, the influence of the previous diet had disappeared. Sibbald (1976b) observed that the quantity of gross energy excreted daily by adult roosters during a fast decreased with the duration of starvation. However, the extension of the period of starvation from 24 to 96 hr, by intervals of 24 hr, had no significant effect on the TME value of a laying hen diet. The work described in this report was conducted to determine the effect of previous intake of protein and cellulose, body weight distribution of the assay bird and the duration of the period of starvation prior to force feeding on the TME value of corn. MATERIALS AND METHODS
1 Present address: Department of Animal and Poultry Science, The University of Saskatchewan, Saskatoon, Saskatchewan S7N OWO, Canada.
602
Experimental Design and Animals. Single Comb White Leghorn (Shaver Starcross 288) roosters were used in the experiments. The birds were housed in individual cages in a
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ABSTRACT Two experiments were conducted with 36 adult White Leghorn roosters to determine the effect of previous intake of protein (Experiment 1) or purified cellulose (Experiment 2), body weight, and duration of starvation of the assay bird on the true metabolizable energy (TME) value of ground yellow corn. The mean TME value (± SE) of the corn was 4.06 ± .03 and 4.06 ± .04 kcal/g of dry matter in Experiment 1 and 2, respectively. Dietary levels of 10, 20, and 30% protein or 0, 7.5, and 15.0% supplementary cellulose, and body weight distribution had no significant (P>.05) effect on the TME value of the corn. Starvation for 12 hr before force feeding resulted in a significant (P<.05) decrease of 4% in the TME value of the corn, whereas fasting periods of 24 or 48 hr had no significant effect. It is suggested that the assay birds be paired on the basis of body weight and starved for a minimum period of 24 hr prior to force feeding to reduce the variation associated with the estimate of TME.
EFFECT OF DIET, WEIGHT, AND FAST ON TME
603
TABLE 1. Composition of diets Composition iaf diets Ingredient
1
4
3
2
\'o) -
83.00
Yellow corn, ground Sucrose Isolated soybean protein a Corn oil DL - methionine
Chemical analysis Crude protein, % AME f , kcal/kg AME/protein ratio Acid detergent fiber, %
65.03 22.36 4.41
53.33 33.54 4.83
7.50 4.00
.10
.20
.30
.05
3.00 2.10 1.00 1.00
2.10 1.50 1.00
Same as diet 1
.80 .05
.90
10.4 3610
20.4 3610
30.3 3610
14.8 3420
347
177
119
231 3.2
Promine-D. Central Soya, Chicago, IL. Alpha-Floe. Brown Co., Berlin, NH. c
Mineral mix supplied the following in g per kg of diet: K H 2 P 0 4 , 10.0; KCl, 1.0; NaCl, 6.0;MnSO 4 - H 2 0 , .35; F e S 0 „ - 7 H 2 0 , .5; MgSO„ (anhydrous), 3.0; K I 0 3 , .01; CuSO„-5H 2 0, .03; ZnC0 3 , .15; CoCl 2 -6H 2 0, .0017; Na 2 MoO 4 -2H 2 O,.0083;Na 2 SeO 3 1 .002. Vitamin mix supplied the following per kg of diet: thiamine HCl, 15 mg; riboflavin, 15 mg; niacin, 50 mg; folic acid, 6 mg; pyridoxine HCl, 6 mg; d-biotin, .6 mg; vitamin B, 2 , 20 Mg; choline chloride, 2000 mg; d-calcium pantothenate, 20 mg; menadione sodium bisulfite, 1.5 mg; vitamin E, 50 IU; vitamin D 3 , 4500 ICU; vitamin A, 9000 IU; ethoxyquin, 125 mg. Dicalcium phosphate contained 18.5% calcium and 20.5% phosphorus. Apparent ME values were calculated.
windowless room. Alternate cages were left vacant to minimize the possibility of cross contamination of excreta. Each cage was fitted with an individual feeder, and between assays feed and water were supplied ad libitum. Room lighting was controlled automatically to provide 14 hr of light and 10 hr of darkness. The roosters used in Experiment 1 were 13 months of age. They were starved overnight and weighed to the nearest 10 g. Birds of similar body weight were paired and 6 pairs of heavy, medium, and light birds were selected. Two pairs of birds from each weight group were assigned to each of the three semipurified diets. The allocation of diets to pairs within a weight group was made on the basis of body weight to equalize the mean body weight of the birds among diets. The composition of the experimental diets is shown in Table 1. Diets 1,2, and 3 were formulated to provide levels of 10, 20,
and 30% of crude protein, respectively. Birds were allowed a period of 10 days to adapt to the diets before the start of the first assay. Fritz et al. (1936) have shown that a period of 3 days is sufficient to overcome any effect of the previous diet on nitrogen excretion in the adult rooster. The assay was repeated at intervals of 4 and 2 weeks to provide three replicates. Prior to an assay, each weight group was starved for 12, 24, or 48 hr, according to a 3 x 3 Latin square design involving body weight groups, fasting periods, and replicates, and then each bird was weighed. A sample of ground yellow corn was assayed for TME by the method described by Sibbald (1976a). The birds used in Experiment 2 were selected from the same population of roosters used in Experiment 1 and were 3 months older. The experimental design and method of assay of the corn meal were identical with those
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Cellulose 0 Mineral mix c Calcium carbonate Vitamin mix0* Dicalcium phosphate e L - lysine -HCl
76.72 11.18 4.00
604
SHIRES ET AL. TABLE 2. Mean daily intake of diets for Experiment 1 and 2 Dietary protein
Experiment
Dietary cellulose
10% 20% 30% 0%
103
97
7.5°/
-(g/bird/day)98 87 88
15%
90
RESULTS AND DISCUSSION Experiment 1. The mean daily intake of the diets and the mean body weight of roosters at the start of the experiment are given in Table 2
TABLE 3.Mean body weight of roosters at the start of the experiments and the effect of previous intake of protein (Experiment 1) or cellulose (Experiment 2), duration offast, body weight distribution, and replication on weight gains or losses between the assays Exp eriment 2
Experiment : Treatment
Initial body wt
Protein or cellulose Low Medium High
NS2 2.63 2.64 2.62
Fast 12 hr 24 hr 48 hr Weight Heavy Medium Light
** * 2.87 a 2.58 b 2.45 c
Replicate 1 2 3 SE (n) 1 Grand mean
.03(12) 2.63
Wt gain or loss
Initial body wt
Wt gain or loss
NS 2.79 2.79 2.77
NS -.03 -.05 -.05
(Kg; ab
.02 .04 a .00 b
* **
* **
.12* -.02 b -.04 b
.03 a -.06 b -.10 c
NS .00 .03 .02
***
*
2.98 a 2.77b 2.61 c
-.06 a -.02 b -.05 a b
* **
** *
-.03 a .08 b .01C
-.09 a -.04 b -.01 b
.01(36) .02
.02(12) 2.79
' ' Means within a column and group with no common letter are significantly different (P<.05). Standard error of a treatment mean (n = no. of observations). NS, nonsignificant. *P<.05. ***P<.001. 1 2
.01(36) -.04
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described for Experiment 1, except that the period of adaptation to the experimental diets was extended from 10 to 24 days and the interval between assays was 2 weeks. The composition of the basal diet (Diet 4) is shown in Table 1. The basal diet was diluted with purified wood cellulose (Alpha-Floe) to provide levels of 0, 7.5, and 15.0% of supplementary cellulose. Analytical Methods. The excreta voided by
each bird during the 24-hr period of assay was collected quantitatively, frozen, freeze-dried, allowed to come to equilibrium with atmospheric moisture, weighed, and finely ground. Samples of the excreta and corn meal were assayed for gross energy by bomb calorimetry and for nitrogen and moisture by the methods described by the AOAC (1970). Statistical Analysis. All data were analyzed by analysis of variance. The experimental design was a 3 X 3 Latin square with repeated measures (Winer, 1971). Where significant treatment effects were demonstrated, NewmanKeuls' test was used to determine the significance of differences between means (Winer, 1971).
EFFECT OF DIET, WEIGHT, AND FAST ON TME
T h e extension of t h e fasting p e r i o d from 12 t o 2 4 hr caused a significant ( P < . 0 5 ) de-
crease in b o d y weight. T h e loss in b o d y weight m a y be related in part t o t h e e m p t y i n g of t h e digestive tract and in p a r t t o t h e depletion of energy and protein reserves during fasting. T h e m e a n b o d y weight of birds decreased during t h e period of a d a p t a t i o n , increased during t h e interval b e t w e e n replicate 1 a n d 2 and was c o n s t a n t for replicate 2 and 3 . T h e main effect of replication was highly significant (P<.001). T h e effect of t r e a t m e n t s on t h e e x c r e t i o n of gross energy b y roosters force fed corn meal or starved a n d on t h e T M E value of t h e corn is s h o w n in Table 4 . It was observed t h a t t h e o u t p u t of excreta energy b y fed a n d unfed birds was directly related t o t h e previous i n t a k e of p r o t e i n . However, t h e effect of d i e t a r y p r o t e i n i n t a k e on t h e e x c r e t a energy o u t p u t of t h e unfed bird was greater a n d highly significant ( P < . 0 0 1 ) as c o m p a r e d t o t h e response
TABLE 4. Effect of previous intake of protein, duration of fast, body weight distribution, and replication on the excretion of gross energy by roosters force fed com meal or starved, and on the true metabolizable energy (TME) value of the com meal Energy output in excreta Treatment
Fed bird
Unfed bird
TME1 (kcal/g)
2
***
Protein 10% 20% 30%
NS 17.94U00) 3 18.37(102) 19.20(107)
7.94(100)2 8.65(109)2 10.31(130) b
Fast 12 hr 24 hr 48 hr
** *
***
21.662 17.68 b 16.17 b
10.582 7.92 b 8.39b
Weight Heavy Medium Light
**
*
20.47 a 17.38 b 17.66 b
10.012 8.57b 8.31 b
Replicate 1 2 3
NS 19.54 17.99 17.98
*
SE" Grand mean
.59 18.50
a
3.992
4.052b 4.14b NS 4.02 4.10 4.07
9.80 a 8.932b 8.17 b
NS 4.05 4.08 4.05
.39 8.96
.03 4.06
' Means within a column and group with no common letter are significantly different (P<.05). Values are expressed on a dry matter basis. 2 NS, nonsignificant. 3 Figures in parentheses are relative values. 4 Standard error of a treatment mean (n = 18). *P<.05. **P<.01. ***P<.001. 1
NS 4.04 4.06 4.09
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a n d 3, respectively. Similar levels of intake were observed for t h e m e d i u m a n d high p r o t e i n diets (Table 2), b u t t h e y did n o t result in similar gains in b o d y weight (Table 3). T h e m e a n b o d y weight of birds fed t h e high protein diet remained c o n s t a n t . In contrast, birds given t h e m e d i u m p r o t e i n diet e x h i b i t e d a small (1.4%) b u t significant ( P < . 0 5 ) increase in b o d y weight. T h e weight gain of birds fed t h e low p r o t e i n diet was less t h a n 1% and nonsignificant ( P > . 0 5 ) . T h e different gains in b o d y weight m a y b e related in part t o t h e differences in t h e ratio of a p p a r e n t metabolizable energy (AME), expressed as kcal per kg of diet, t o t h e percentage of crude p r o t e i n in t h e diets (Table 1). T h e e n e r g y : p r o t e i n ratios of t h e low, m e d i u m , and high p r o t e i n diets were 347, 177, and 119, respectively.
605
606
SHIRES ETAL.
TABLE 5. Effect of previous intake of protein, duration of fast, body weight distribution, and replication on the excretion of nitrogen (N) by roosters force fed com meal or starved Nitrogen output in excreta Treatment
Fed bird
Unfed bird
Protein 10% 20% 30%
** *
.599(100)* .708(118) b .824(138) c
.516(10O) a .623(121)b .745(144) c
Fast 12 hr 24 hr 48 hr
,768 a .662b .701 b
**
NS2 .662 .577 .646
Weight Heavy Medium Light
*
*
.766 a .667b .698b
.684 a .603 b .597 b
Replicate 1 2 3
*#* .811 a .663 b .657b
NS 2 .670 .616 .599
SE1 Grand mean
.022 .710
.025 .628
(g N/bird/24 hr)
** *
' ' Means within a column and group with no common letter are significantly different (P<.05). Figures in parentheses are relative values. 'Standard error of a treatment mean (n = 18). 2 NS, nonsignificant. *P<.05. **P<.01. ***P<.001.
in the TME value of the corn. The difference between the 12 and 48-hr fast in the TME values was significant (P<.05). The output of excreta energy by roosters was found to vary with body weight. The heavy group of fed and unfed birds excreted significantly (P<.05) more gross energy than the medium and light groups. This effect was in part a reflection of the bias in body weight distribution between groups. The difference in mean body weight between the medium and light group was only .13 kg, whereas the heavy group weighed .30 kg more than the medium group. Since the assay of TME involved the pairing of birds of similar body weight (Sibbald, 1976a), the TME value of the corn was not significantly affected by the body weight distribution. The effect of treatments on the excretion of nitrogen by roosters force fed corn meal or starved is shown in Table 5. A comparison of the data presented in Table 4 and 5 indicated that nitrogen and gross energy output were directly related and this was confirmed by correlation analysis. The correlation coefficients (r) between nitrogen and gross energy output for the fed (r = .61) and unfed (r = .83) birds were highly significant (P<.01). The data indicated that the quantity of nitrogen and gross energy excreted by fed and unfed birds was related to the previous intake of protein, the duration of starvation prior to force feeding, and the body weight distribution. It was noted previously that protein intake had a much greater effect on the excreta energy output of the unfed bird as compared to the fed bird (Table 4). In contrast, the increments in nitrogen output in response to increases in protein intake were approximately equal for the fed and unfed birds (Table 5). It was observed that replicate 1 was associated with greater outputs of nitrogen and gross energy than replicate 2 and 3 (Table 4 and 5). The nitrogen output of the fed and unfed birds decreased by about 18 and 8%, respectively, from replicate 1 to 2 and was constant for replicate 2 and 3. The response may reflect a metabolic adaptation to the program of feeding and fasting or to changes in the physiological state of the birds. The roosters were observed to pass through a partial molt during the initial half of the experiment. Ackerson et al. (1926) reported that the excretion of endogenous nitrogen by mature hens was increased during a molt.
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of the fed bird which was relatively small and nonsignificant. The relative changes in excreta energy output with dietary protein level are shown in parentheses. The differential response of the fed and unfed birds resulted in a small but nonsignificant increase in the TME value of the corn and may be related to the sparing effect of the corn on the utilization of energy and labile protein reserves (Munro, 1951). The excreta energy output of the fed and unfed birds decreased significantly (P<.05) in response to extension of the fasting period from 12 to 24 hr. An additional fast of 24 hr resulted in a smaller and nonsignificant decrease in the excreta energy output of the fed bird and a slight increase in the excreta energy output of the unfed bird. The extension of the fasting period from 12 to 24 hr or 48 hr was associated with increases of 1.5 and 3.8%, respectively,
EFFECT OF DIET, WEIGHT, AND FAST ON TME
TABLE 6. Effect of previous intake of cellulose, duration of fast, body weight distribution, and replication on the excretion of gross energy by roosters force fed corn meal or starved, and on the true metabolizable energy (TME) value of the corn meal Energy output in excreta Unfed bird
TME1
Treatment
Fed bird
Cellulose 0% 7.5% 15.0%
NS 3 19.16 19.08 20.52
Fast 12 hr 24 hr 48 hr
***
**
23.60 a 18.12b 17.03 b
10.96 a 8.97b 7.88 b
3.96 a 4.12b 4.12b
Weight Heavy Medium Light
NS 20.88 19.06 18.80
NS 8.92 9.57 9.33
NS 3.99 4.10 4.10
Replicate 1 2 3
NS 18.72 19.49 20.54
NS 9.16 9.42 9.24
NS 4.10 4.07 4.02
SE2 Grand mean
.73 19.58
.55 9.27
.04 4.06
(kcal/bird/24 hr) NS 9.78 9.64 8.39
(kcal/g) NS 4.11 4.10 3.98
*
' Means within a column and group with no common letter are significantly different (P<.05). 1 Values are expressed on a dry matter basis. 2 Standard error of a treatment mean (n = 18). 3 NS, nonsignificant. *P<.05. **P<.01. ***P<.001.
to the duration of the fasting period. A similar response to fasting was observed in Experiment 1. The effect of treatments on the excreta energy output of roosters force fed corn meal or starved and on the TME value of the corn is shown in Table 6. Two of the unfed birds previously given the low cellulose diet and then fasted for 12 hr excreted considerably more gross energy than their force-fed partners. This discrepancy resulted in TME values which exceeded the gross energy content of the corn. The inconsistent values were omitted from the data and replaced by the value obtained for the unfed bird of the second pair within the cells. The effects of previous intake of cellulose, body weight distribution, and replication on excreta energy losses and TME values were nonsignificant. It was observed that the fed and unfed birds excreted significantly (P<.05) more gross energy following a fast of 12 hr than after fasting for 24 or 48 hr (Table 6). The greater outputs of excreta energy were associated with a significant (P<.05) decrease of 3.8% in the TME value of the corn. A similar response to fasting was observed in Experiment 1 (Table 4). Fasting periods of 12, 24, and 48 hr before force feeding resulted in mean TME values of 3.99, 4.05, and 4.14 kcal/g, respectively, in Experiment 1 and for the same periods in Experiment 2, mean TME values of 3.96, 4.12, and 4.12 kcal/g. The data indicate that fasting periods of less than 24 hr resulted in a significant (P<.05) decrease in the TME value of the corn and that starvation for periods of 24 or 48 hr had no significant effect. The results of this study are in agreement with the report of Sibbald (1976b). He observed that the quantity of gross energy excreted daily by adult roosters during a fast decreased with the duration of starvation. However, the extension of the fasting period from 24 to 96 hr, by intervals of 24 hr, had no significant effect on the TME value of a laying hen diet. The mean TME value (± SE) of the corn was 4.06 ± .03 and 4.06 ± .04 kcal/g of dry matter in Experiment 1 and 2, respectively. Sibbald (1977) reported that the TME values of 16 samples of yellow corn ranged between 3.98 and 4,32 kcal/g of dry matter, with a mean value of 4.12 kcal/g. It appears that the TME values of feedstuffs are reproducible within and between laboratories and are not significantly affected by the previous diet.
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Experiment 2. The mean daily intake of the medium and high cellulose diet was greater by 1 and 3%, respectively, than the intake of the low cellulose diet (Table 2). It is evident that the birds failed to adjust their feed intake to compensate for the dilution in the energy concentration of the diets with cellulose. The lack of response was not expected, since birds fed the same diets in a preliminary trial did adapt their feed intake to maintain a constant level of energy intake. All diets were associated with a decrease in body weight, but the weight losses were small (1 to 2%) and nonsignificant (Table 3). It was found that weight losses were greatest during the period of adaptation and were proportional
607
608
SHIRES ETAL.
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.
REFERENCES Ackerson, C. W., M. J. Blish, and F. E. Mussehl, 1926. The endogenous nitrogen of hens as affected by molting. Poultry Sci. 5:153-161. Association of Official Analytical Chemists, 1970. Official methods of analysis. 11th ed. Ass. Off. Anal. Chem., Washington, DC. Fritz, J. C , W. A. Hendricks, and H. W. Titus, 1936. The influence of previous feeding on the nitrogen excretion of fasting birds. Amer. J. Physiol. 115: 281-286. Munro, H. N., 1951. Carbohydrate and fat as factors in protein utilization and metabolism. Physiol. Rev. 31:449-488. Sibbald, I. R., 1976a. A bioassay for true metabolizable energy in feedingstuffs. Poultry Sci. 55:SOSSOS. Sibbald, I. R., 1976b. The effect of the duration of starvation of the assay bird on true metabolizable energy values. Poultry Sci. 55.1578-1579. Sibbald, I. R., 1977. The true metabolizable energy values of some feedingstuffs. Poultry Sci. 56:380— 382. Winer, B. J., 1971. Statistical principles in experimental design. 2nd ed. McGraw-Hill Book Co., Inc., New York, NY.
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It may be concluded that the previous intake of protein or purified cellulose, and body weight distribution of the assay bird had no significant effect on the TME value of corn. Fasting periods of less than 24 hr before force feeding resulted in a significant (P<.05) decrease in the TME value of corn, whereas starvation for periods of 24 or 48 hr had no significant effect. It is suggested that the assay birds be paired on the basis of body weight and starved for a minimum period of 24 hr prior to force feeding to reduce the variation associated with the estimate of TME.
1979 Poultry Science 58:602-608
INTRODUCTION
The bioassay developed by Sibbald (1976a) to measure the true metabolizable energy (TME) value of feedstuffs involves the force feeding of adult roosters with the material under test and the total collection of excreta. Prior to an assay, birds of similar body weight are paired and starved to empty their digestive tracts. After a fast of 21 hr, one member of each pair of birds is force fed a sample (ca. 25 g) of the feedstuff and the second member of the pair is starved. The excreta voided by each bird during the following period of 24 hr is collected quantitatively, dried, weighed, and analyzed for gross energy content. The TME value of the feedstuff is calculated as the difference between gross energy of the feed intake and gross energy of the excreta of the fed bird after correction of the latter for metabolic fecal energy ( F E m ) and endogenous urinary energy (UE e ). It is assumed that the excreta energy voided by the unfed bird provides a valid estimate of the F E m + UE e losses of the fed bird. The assay measures the TME value of a feedstuff when fed singly at
levels of intake below the maintenance requirement for energy. It is possible that the previous intake of protein and energy and the duration of the period of starvation prior to force feeding may influence the estimates of TME. Fritz et al. (1936) reported that the quantity of nitrogen excreted daily by adult roosters during a fast was related initially to the previous intake of protein until, on the third day of fasting, the influence of the previous diet had disappeared. Sibbald (1976b) observed that the quantity of gross energy excreted daily by adult roosters during a fast decreased with the duration of starvation. However, the extension of the period of starvation from 24 to 96 hr, by intervals of 24 hr, had no significant effect on the TME value of a laying hen diet. The work described in this report was conducted to determine the effect of previous intake of protein and cellulose, body weight distribution of the assay bird and the duration of the period of starvation prior to force feeding on the TME value of corn. MATERIALS AND METHODS
1 Present address: Department of Animal and Poultry Science, The University of Saskatchewan, Saskatoon, Saskatchewan S7N OWO, Canada.
602
Experimental Design and Animals. Single Comb White Leghorn (Shaver Starcross 288) roosters were used in the experiments. The birds were housed in individual cages in a
Downloaded from http://ps.oxfordjournals.org/ at UNIVERSITY OF AUCKLAND LIBRARY on April 23, 2015
ABSTRACT Two experiments were conducted with 36 adult White Leghorn roosters to determine the effect of previous intake of protein (Experiment 1) or purified cellulose (Experiment 2), body weight, and duration of starvation of the assay bird on the true metabolizable energy (TME) value of ground yellow corn. The mean TME value (± SE) of the corn was 4.06 ± .03 and 4.06 ± .04 kcal/g of dry matter in Experiment 1 and 2, respectively. Dietary levels of 10, 20, and 30% protein or 0, 7.5, and 15.0% supplementary cellulose, and body weight distribution had no significant (P>.05) effect on the TME value of the corn. Starvation for 12 hr before force feeding resulted in a significant (P<.05) decrease of 4% in the TME value of the corn, whereas fasting periods of 24 or 48 hr had no significant effect. It is suggested that the assay birds be paired on the basis of body weight and starved for a minimum period of 24 hr prior to force feeding to reduce the variation associated with the estimate of TME.
EFFECT OF DIET, WEIGHT, AND FAST ON TME
603
TABLE 1. Composition of diets Composition iaf diets Ingredient
1
4
3
2
\'o) -
83.00
Yellow corn, ground Sucrose Isolated soybean protein a Corn oil DL - methionine
Chemical analysis Crude protein, % AME f , kcal/kg AME/protein ratio Acid detergent fiber, %
65.03 22.36 4.41
53.33 33.54 4.83
7.50 4.00
.10
.20
.30
.05
3.00 2.10 1.00 1.00
2.10 1.50 1.00
Same as diet 1
.80 .05
.90
10.4 3610
20.4 3610
30.3 3610
14.8 3420
347
177
119
231 3.2
Promine-D. Central Soya, Chicago, IL. Alpha-Floe. Brown Co., Berlin, NH. c
Mineral mix supplied the following in g per kg of diet: K H 2 P 0 4 , 10.0; KCl, 1.0; NaCl, 6.0;MnSO 4 - H 2 0 , .35; F e S 0 „ - 7 H 2 0 , .5; MgSO„ (anhydrous), 3.0; K I 0 3 , .01; CuSO„-5H 2 0, .03; ZnC0 3 , .15; CoCl 2 -6H 2 0, .0017; Na 2 MoO 4 -2H 2 O,.0083;Na 2 SeO 3 1 .002. Vitamin mix supplied the following per kg of diet: thiamine HCl, 15 mg; riboflavin, 15 mg; niacin, 50 mg; folic acid, 6 mg; pyridoxine HCl, 6 mg; d-biotin, .6 mg; vitamin B, 2 , 20 Mg; choline chloride, 2000 mg; d-calcium pantothenate, 20 mg; menadione sodium bisulfite, 1.5 mg; vitamin E, 50 IU; vitamin D 3 , 4500 ICU; vitamin A, 9000 IU; ethoxyquin, 125 mg. Dicalcium phosphate contained 18.5% calcium and 20.5% phosphorus. Apparent ME values were calculated.
windowless room. Alternate cages were left vacant to minimize the possibility of cross contamination of excreta. Each cage was fitted with an individual feeder, and between assays feed and water were supplied ad libitum. Room lighting was controlled automatically to provide 14 hr of light and 10 hr of darkness. The roosters used in Experiment 1 were 13 months of age. They were starved overnight and weighed to the nearest 10 g. Birds of similar body weight were paired and 6 pairs of heavy, medium, and light birds were selected. Two pairs of birds from each weight group were assigned to each of the three semipurified diets. The allocation of diets to pairs within a weight group was made on the basis of body weight to equalize the mean body weight of the birds among diets. The composition of the experimental diets is shown in Table 1. Diets 1,2, and 3 were formulated to provide levels of 10, 20,
and 30% of crude protein, respectively. Birds were allowed a period of 10 days to adapt to the diets before the start of the first assay. Fritz et al. (1936) have shown that a period of 3 days is sufficient to overcome any effect of the previous diet on nitrogen excretion in the adult rooster. The assay was repeated at intervals of 4 and 2 weeks to provide three replicates. Prior to an assay, each weight group was starved for 12, 24, or 48 hr, according to a 3 x 3 Latin square design involving body weight groups, fasting periods, and replicates, and then each bird was weighed. A sample of ground yellow corn was assayed for TME by the method described by Sibbald (1976a). The birds used in Experiment 2 were selected from the same population of roosters used in Experiment 1 and were 3 months older. The experimental design and method of assay of the corn meal were identical with those
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Cellulose 0 Mineral mix c Calcium carbonate Vitamin mix0* Dicalcium phosphate e L - lysine -HCl
76.72 11.18 4.00
604
SHIRES ET AL. TABLE 2. Mean daily intake of diets for Experiment 1 and 2 Dietary protein
Experiment
Dietary cellulose
10% 20% 30% 0%
103
97
7.5°/
-(g/bird/day)98 87 88
15%
90
RESULTS AND DISCUSSION Experiment 1. The mean daily intake of the diets and the mean body weight of roosters at the start of the experiment are given in Table 2
TABLE 3.Mean body weight of roosters at the start of the experiments and the effect of previous intake of protein (Experiment 1) or cellulose (Experiment 2), duration offast, body weight distribution, and replication on weight gains or losses between the assays Exp eriment 2
Experiment : Treatment
Initial body wt
Protein or cellulose Low Medium High
NS2 2.63 2.64 2.62
Fast 12 hr 24 hr 48 hr Weight Heavy Medium Light
** * 2.87 a 2.58 b 2.45 c
Replicate 1 2 3 SE (n) 1 Grand mean
.03(12) 2.63
Wt gain or loss
Initial body wt
Wt gain or loss
NS 2.79 2.79 2.77
NS -.03 -.05 -.05
(Kg; ab
.02 .04 a .00 b
* **
* **
.12* -.02 b -.04 b
.03 a -.06 b -.10 c
NS .00 .03 .02
***
*
2.98 a 2.77b 2.61 c
-.06 a -.02 b -.05 a b
* **
** *
-.03 a .08 b .01C
-.09 a -.04 b -.01 b
.01(36) .02
.02(12) 2.79
' ' Means within a column and group with no common letter are significantly different (P<.05). Standard error of a treatment mean (n = no. of observations). NS, nonsignificant. *P<.05. ***P<.001. 1 2
.01(36) -.04
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described for Experiment 1, except that the period of adaptation to the experimental diets was extended from 10 to 24 days and the interval between assays was 2 weeks. The composition of the basal diet (Diet 4) is shown in Table 1. The basal diet was diluted with purified wood cellulose (Alpha-Floe) to provide levels of 0, 7.5, and 15.0% of supplementary cellulose. Analytical Methods. The excreta voided by
each bird during the 24-hr period of assay was collected quantitatively, frozen, freeze-dried, allowed to come to equilibrium with atmospheric moisture, weighed, and finely ground. Samples of the excreta and corn meal were assayed for gross energy by bomb calorimetry and for nitrogen and moisture by the methods described by the AOAC (1970). Statistical Analysis. All data were analyzed by analysis of variance. The experimental design was a 3 X 3 Latin square with repeated measures (Winer, 1971). Where significant treatment effects were demonstrated, NewmanKeuls' test was used to determine the significance of differences between means (Winer, 1971).
EFFECT OF DIET, WEIGHT, AND FAST ON TME
T h e extension of t h e fasting p e r i o d from 12 t o 2 4 hr caused a significant ( P < . 0 5 ) de-
crease in b o d y weight. T h e loss in b o d y weight m a y be related in part t o t h e e m p t y i n g of t h e digestive tract and in p a r t t o t h e depletion of energy and protein reserves during fasting. T h e m e a n b o d y weight of birds decreased during t h e period of a d a p t a t i o n , increased during t h e interval b e t w e e n replicate 1 a n d 2 and was c o n s t a n t for replicate 2 and 3 . T h e main effect of replication was highly significant (P<.001). T h e effect of t r e a t m e n t s on t h e e x c r e t i o n of gross energy b y roosters force fed corn meal or starved a n d on t h e T M E value of t h e corn is s h o w n in Table 4 . It was observed t h a t t h e o u t p u t of excreta energy b y fed a n d unfed birds was directly related t o t h e previous i n t a k e of p r o t e i n . However, t h e effect of d i e t a r y p r o t e i n i n t a k e on t h e e x c r e t a energy o u t p u t of t h e unfed bird was greater a n d highly significant ( P < . 0 0 1 ) as c o m p a r e d t o t h e response
TABLE 4. Effect of previous intake of protein, duration of fast, body weight distribution, and replication on the excretion of gross energy by roosters force fed com meal or starved, and on the true metabolizable energy (TME) value of the com meal Energy output in excreta Treatment
Fed bird
Unfed bird
TME1 (kcal/g)
2
***
Protein 10% 20% 30%
NS 17.94U00) 3 18.37(102) 19.20(107)
7.94(100)2 8.65(109)2 10.31(130) b
Fast 12 hr 24 hr 48 hr
** *
***
21.662 17.68 b 16.17 b
10.582 7.92 b 8.39b
Weight Heavy Medium Light
**
*
20.47 a 17.38 b 17.66 b
10.012 8.57b 8.31 b
Replicate 1 2 3
NS 19.54 17.99 17.98
*
SE" Grand mean
.59 18.50
a
3.992
4.052b 4.14b NS 4.02 4.10 4.07
9.80 a 8.932b 8.17 b
NS 4.05 4.08 4.05
.39 8.96
.03 4.06
' Means within a column and group with no common letter are significantly different (P<.05). Values are expressed on a dry matter basis. 2 NS, nonsignificant. 3 Figures in parentheses are relative values. 4 Standard error of a treatment mean (n = 18). *P<.05. **P<.01. ***P<.001. 1
NS 4.04 4.06 4.09
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a n d 3, respectively. Similar levels of intake were observed for t h e m e d i u m a n d high p r o t e i n diets (Table 2), b u t t h e y did n o t result in similar gains in b o d y weight (Table 3). T h e m e a n b o d y weight of birds fed t h e high protein diet remained c o n s t a n t . In contrast, birds given t h e m e d i u m p r o t e i n diet e x h i b i t e d a small (1.4%) b u t significant ( P < . 0 5 ) increase in b o d y weight. T h e weight gain of birds fed t h e low p r o t e i n diet was less t h a n 1% and nonsignificant ( P > . 0 5 ) . T h e different gains in b o d y weight m a y b e related in part t o t h e differences in t h e ratio of a p p a r e n t metabolizable energy (AME), expressed as kcal per kg of diet, t o t h e percentage of crude p r o t e i n in t h e diets (Table 1). T h e e n e r g y : p r o t e i n ratios of t h e low, m e d i u m , and high p r o t e i n diets were 347, 177, and 119, respectively.
605
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SHIRES ETAL.
TABLE 5. Effect of previous intake of protein, duration of fast, body weight distribution, and replication on the excretion of nitrogen (N) by roosters force fed com meal or starved Nitrogen output in excreta Treatment
Fed bird
Unfed bird
Protein 10% 20% 30%
** *
.599(100)* .708(118) b .824(138) c
.516(10O) a .623(121)b .745(144) c
Fast 12 hr 24 hr 48 hr
,768 a .662b .701 b
**
NS2 .662 .577 .646
Weight Heavy Medium Light
*
*
.766 a .667b .698b
.684 a .603 b .597 b
Replicate 1 2 3
*#* .811 a .663 b .657b
NS 2 .670 .616 .599
SE1 Grand mean
.022 .710
.025 .628
(g N/bird/24 hr)
** *
' ' Means within a column and group with no common letter are significantly different (P<.05). Figures in parentheses are relative values. 'Standard error of a treatment mean (n = 18). 2 NS, nonsignificant. *P<.05. **P<.01. ***P<.001.
in the TME value of the corn. The difference between the 12 and 48-hr fast in the TME values was significant (P<.05). The output of excreta energy by roosters was found to vary with body weight. The heavy group of fed and unfed birds excreted significantly (P<.05) more gross energy than the medium and light groups. This effect was in part a reflection of the bias in body weight distribution between groups. The difference in mean body weight between the medium and light group was only .13 kg, whereas the heavy group weighed .30 kg more than the medium group. Since the assay of TME involved the pairing of birds of similar body weight (Sibbald, 1976a), the TME value of the corn was not significantly affected by the body weight distribution. The effect of treatments on the excretion of nitrogen by roosters force fed corn meal or starved is shown in Table 5. A comparison of the data presented in Table 4 and 5 indicated that nitrogen and gross energy output were directly related and this was confirmed by correlation analysis. The correlation coefficients (r) between nitrogen and gross energy output for the fed (r = .61) and unfed (r = .83) birds were highly significant (P<.01). The data indicated that the quantity of nitrogen and gross energy excreted by fed and unfed birds was related to the previous intake of protein, the duration of starvation prior to force feeding, and the body weight distribution. It was noted previously that protein intake had a much greater effect on the excreta energy output of the unfed bird as compared to the fed bird (Table 4). In contrast, the increments in nitrogen output in response to increases in protein intake were approximately equal for the fed and unfed birds (Table 5). It was observed that replicate 1 was associated with greater outputs of nitrogen and gross energy than replicate 2 and 3 (Table 4 and 5). The nitrogen output of the fed and unfed birds decreased by about 18 and 8%, respectively, from replicate 1 to 2 and was constant for replicate 2 and 3. The response may reflect a metabolic adaptation to the program of feeding and fasting or to changes in the physiological state of the birds. The roosters were observed to pass through a partial molt during the initial half of the experiment. Ackerson et al. (1926) reported that the excretion of endogenous nitrogen by mature hens was increased during a molt.
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of the fed bird which was relatively small and nonsignificant. The relative changes in excreta energy output with dietary protein level are shown in parentheses. The differential response of the fed and unfed birds resulted in a small but nonsignificant increase in the TME value of the corn and may be related to the sparing effect of the corn on the utilization of energy and labile protein reserves (Munro, 1951). The excreta energy output of the fed and unfed birds decreased significantly (P<.05) in response to extension of the fasting period from 12 to 24 hr. An additional fast of 24 hr resulted in a smaller and nonsignificant decrease in the excreta energy output of the fed bird and a slight increase in the excreta energy output of the unfed bird. The extension of the fasting period from 12 to 24 hr or 48 hr was associated with increases of 1.5 and 3.8%, respectively,
EFFECT OF DIET, WEIGHT, AND FAST ON TME
TABLE 6. Effect of previous intake of cellulose, duration of fast, body weight distribution, and replication on the excretion of gross energy by roosters force fed corn meal or starved, and on the true metabolizable energy (TME) value of the corn meal Energy output in excreta Unfed bird
TME1
Treatment
Fed bird
Cellulose 0% 7.5% 15.0%
NS 3 19.16 19.08 20.52
Fast 12 hr 24 hr 48 hr
***
**
23.60 a 18.12b 17.03 b
10.96 a 8.97b 7.88 b
3.96 a 4.12b 4.12b
Weight Heavy Medium Light
NS 20.88 19.06 18.80
NS 8.92 9.57 9.33
NS 3.99 4.10 4.10
Replicate 1 2 3
NS 18.72 19.49 20.54
NS 9.16 9.42 9.24
NS 4.10 4.07 4.02
SE2 Grand mean
.73 19.58
.55 9.27
.04 4.06
(kcal/bird/24 hr) NS 9.78 9.64 8.39
(kcal/g) NS 4.11 4.10 3.98
*
' Means within a column and group with no common letter are significantly different (P<.05). 1 Values are expressed on a dry matter basis. 2 Standard error of a treatment mean (n = 18). 3 NS, nonsignificant. *P<.05. **P<.01. ***P<.001.
to the duration of the fasting period. A similar response to fasting was observed in Experiment 1. The effect of treatments on the excreta energy output of roosters force fed corn meal or starved and on the TME value of the corn is shown in Table 6. Two of the unfed birds previously given the low cellulose diet and then fasted for 12 hr excreted considerably more gross energy than their force-fed partners. This discrepancy resulted in TME values which exceeded the gross energy content of the corn. The inconsistent values were omitted from the data and replaced by the value obtained for the unfed bird of the second pair within the cells. The effects of previous intake of cellulose, body weight distribution, and replication on excreta energy losses and TME values were nonsignificant. It was observed that the fed and unfed birds excreted significantly (P<.05) more gross energy following a fast of 12 hr than after fasting for 24 or 48 hr (Table 6). The greater outputs of excreta energy were associated with a significant (P<.05) decrease of 3.8% in the TME value of the corn. A similar response to fasting was observed in Experiment 1 (Table 4). Fasting periods of 12, 24, and 48 hr before force feeding resulted in mean TME values of 3.99, 4.05, and 4.14 kcal/g, respectively, in Experiment 1 and for the same periods in Experiment 2, mean TME values of 3.96, 4.12, and 4.12 kcal/g. The data indicate that fasting periods of less than 24 hr resulted in a significant (P<.05) decrease in the TME value of the corn and that starvation for periods of 24 or 48 hr had no significant effect. The results of this study are in agreement with the report of Sibbald (1976b). He observed that the quantity of gross energy excreted daily by adult roosters during a fast decreased with the duration of starvation. However, the extension of the fasting period from 24 to 96 hr, by intervals of 24 hr, had no significant effect on the TME value of a laying hen diet. The mean TME value (± SE) of the corn was 4.06 ± .03 and 4.06 ± .04 kcal/g of dry matter in Experiment 1 and 2, respectively. Sibbald (1977) reported that the TME values of 16 samples of yellow corn ranged between 3.98 and 4,32 kcal/g of dry matter, with a mean value of 4.12 kcal/g. It appears that the TME values of feedstuffs are reproducible within and between laboratories and are not significantly affected by the previous diet.
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Experiment 2. The mean daily intake of the medium and high cellulose diet was greater by 1 and 3%, respectively, than the intake of the low cellulose diet (Table 2). It is evident that the birds failed to adjust their feed intake to compensate for the dilution in the energy concentration of the diets with cellulose. The lack of response was not expected, since birds fed the same diets in a preliminary trial did adapt their feed intake to maintain a constant level of energy intake. All diets were associated with a decrease in body weight, but the weight losses were small (1 to 2%) and nonsignificant (Table 3). It was found that weight losses were greatest during the period of adaptation and were proportional
607
608
SHIRES ETAL.
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.
REFERENCES Ackerson, C. W., M. J. Blish, and F. E. Mussehl, 1926. The endogenous nitrogen of hens as affected by molting. Poultry Sci. 5:153-161. Association of Official Analytical Chemists, 1970. Official methods of analysis. 11th ed. Ass. Off. Anal. Chem., Washington, DC. Fritz, J. C , W. A. Hendricks, and H. W. Titus, 1936. The influence of previous feeding on the nitrogen excretion of fasting birds. Amer. J. Physiol. 115: 281-286. Munro, H. N., 1951. Carbohydrate and fat as factors in protein utilization and metabolism. Physiol. Rev. 31:449-488. Sibbald, I. R., 1976a. A bioassay for true metabolizable energy in feedingstuffs. Poultry Sci. 55:SOSSOS. Sibbald, I. R., 1976b. The effect of the duration of starvation of the assay bird on true metabolizable energy values. Poultry Sci. 55.1578-1579. Sibbald, I. R., 1977. The true metabolizable energy values of some feedingstuffs. Poultry Sci. 56:380— 382. Winer, B. J., 1971. Statistical principles in experimental design. 2nd ed. McGraw-Hill Book Co., Inc., New York, NY.
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It may be concluded that the previous intake of protein or purified cellulose, and body weight distribution of the assay bird had no significant effect on the TME value of corn. Fasting periods of less than 24 hr before force feeding resulted in a significant (P<.05) decrease in the TME value of corn, whereas starvation for periods of 24 or 48 hr had no significant effect. It is suggested that the assay birds be paired on the basis of body weight and starved for a minimum period of 24 hr prior to force feeding to reduce the variation associated with the estimate of TME.