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Effects of Level of Feed Input, Dilution of Test Material, and Duration of Excreta Collection on True Metabolizable Energy Values1
Effects of Level of Feed Input, Dilution of Test Material, and Duration of Excreta Collection on True Metabolizable Energy Values1 I. R. SIBBALD Animal Research Institute, Agriculture Canada, Central Experimental Farm, Ottawa, Ontario, Canada K1A 0C6 (Received for publication December 7,1978)
1979 Poultry Science 58:1325-1329 INTRODUCTION The rate of passage of feed residues through the alimentary canal can be important in some bioassays. The assays for true metabolizable energy (TME) (Sibbald, 1976) and true available amino acids (Sibbald, 1979a) involve force-feeding starved birds and collecting the excreta voided during the subsequent 24 hr. However, there is evidence that the residues of some feedingstuffs take more than 24 hr to clear the alimentary canal (Sibbald, 1978a, 1979b; Jones and Sibbald, 1979). If the residues do not clear the canal within the collection period the observed TME values are too large. The problem can be overcome by extending the excreta collection period (Sibbald, 1979c) but this lengthens the time of the assay. The experiments described in this report were designed to investigate two possible procedures for ensuring complete clearance of feed residues within 24 hr of feeding. The first experiment involved feeding graded levels of feedingstuffs to determine if rate of passage was related to feed input. Sibbald (1979a) fed graded levels of a turkey diet and observed no effect of input level on TME values; however, there was no reason to suspect a slow rate of passage. The second experiment involved measuring the TME
Contribution No. 810, Animal Research Institute.
values of feedingstuffs fed alone and in combination with a diluent known to have a rate of passage of less than 24 hr. Diluents have been used in TME bioassays of rapeseed products (Sibbald, 1977b; Jones and Sibbald, 1979) and it is usual to assay fats in conjunction with a basal diet (Sibbald and Kramer, 1977; Sibbald, 1978b). MATERIALS AND METHODS Experiment 1. Four feedingstuffs were each fed at three levels to adult, Single Comb White Leghorn cockerels which had been starved for 24 hr. Seven birds were assigned to each treatment. Seven additional birds, which received no feed, served as negative controls for the measurement of metabolic plus endogenous energy excretion. The feedingstuffs, which were placed directly into the crops of the birds, were wheat, meat meal, fish meal, and dehydrated alfalfa. Their proximate compositions are presented in Table 1. The levels of input were 10, 20, and 30 g of air dry material per bird. The time of force-feeding was recorded for each bird and the excreta voided from 0 to 24 hr, and from 24 to 48 hr post-feeding was collected quantitatively. The excreta samples were frozen, freeze-dried, equilibrated with atmospheric moisture, and weighed. Samples of the feed and excreta were assayed for gross energy content with an adiabatic oxygen bomb calorimeter.
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ABSTRACT Adult, Leghorn cockerels were used in two bioassays designed to study the effect of 24 and 48 hr excreta collection periods on true metabolizable energy (TME) values of feedingstuffs. In the first experiment, 4 feedingstuffs were each evaluated at input levels of 10,20, and 30 g/bird. In the second assay 3 feedingstuffs were fed alone and as blends with a carrier. A reduction in TME value associated with extension of the excreta collection period was evidence that feed residues had not cleared the alimentary canal within 24 hr. Residues of wheat and of the carrier cleared the canal within 24 hr while those of fish meal were almost cleared. Residues of dehydrated alfalfa and, to a lesser extent, meat meal required a longer period. Varying input levels, and dilution with a carrier, had minor effects on clearance times. It is concluded that the duration of the excreta collection period must be adjusted according to the rate of passage of the material being assayed. Reduction in input or blending with a carrier were not satisfactory solutions to the problems of slow residue clearance.
SIBBALD
1326
TABLE 1. Proximate compositions of the feedingstuffs (% of dry matter) and gross energy content (kcal/g)
Wheat
Meat meal
Fish meal
Dehydrated alfalfa
.4.7 2.77 3.86 2.30 4.43
52.8 9.86 4.34 25.90 4,23
60.6 7.28 .54 24.56 4.37
15.9 3.40 29.10 9.10 4.44
Crude protein (N X 6.25) Ether extract Crude fiber Ash Gross energy
TABLE 2. Compositions of the feedingstuffs assayed in Experiment 2 (g)
Feedingstuff
Basal diet 3
1 2 3 4 5 6 7 8 9 10
30 0 10 20 0 10 20 0 10 20
Dehyhydrated alfalfa^
Meat meal b
Fish meal b
30 20 10 30 20 10
95% Ground wheat + 5% tallow. For composition see Table 1.
30 20 10
used in Experiment 1. The TME values of the dehydrated alfalfa, meat meal, and fish meal based on 24 and 48 hr of excreta collection were determined. When these materials were fed as mixtures their values were calculated by difference using the appropriate mean values for the basal diet. The data were subjected to an analysis of variance using a split plot design.
RESULTS AND DISCUSSION The mean TME values of Experiment 1 are displayed in Table 3. The duration of the excreta collection period had no effect upon the TME values of wheat indicating that the undigested residues cleared the alimentary canal within 24 hr. It is interesting to note that the overall mean value for the wheat (3.83 kcal/g) is similar to the value of 3.80 kcal/g obtained when wheat drawn from the same lot was assayed in an earlier experiment (Sibbald, 1979c). The TME values of meat meal and fish meal decreased slightly when the excretion collection period was extended from 24 to 48 hr suggesting that some residues had not cleared the alimentary canal within 24 hr. The differences were small and of questionable practical significance. In an earlier study of rate of passage, residues of meat meal and fish meal took longer than 24 hr to clear the alimentary canal (Sibbald, 1979b), but the findings are not directly comparable because the origins of the samples were different. The TME values of the alfalfa decreased markedly as the duration of the excreta collection period was extended demonstrating that residues remained in the alimentary canal for more than 24 hr. This confirms the observations of Sibbald (1979b,c). The 48 hr TME values of wheat and meat meal appeared to decrease slightly as the level of input increased. There is no apparent biologi-
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The energy excreted per bird for the periods 0 to 24 and 0 to 48 hr post-feeding were calculated. The resulting data, together with the gross energy values of the feeds, were used to calculate TME values for each feed fed to each bird for two excreta collection periods. The TME data were subjected to an analysis of variance using a split plot deisgn. The latter was necessary because the two values obtained with each bird were not independent. Experiment 2. Ten feedingstuffs were assayed for TME content using similar procedures to those described above. Eight birds were assigned to each feedingstuff. Feed inputs were held constant at 30 g/bird. The feedingstuffs are described in Table 2. The basal diet consisted primarily of wheat which is known to clear the alimentary canal within 24 hr (Experiment 1). Fat was added to reduce dustiness and to facilitate force-feeding. The dehydrated alfalfa, meat meal, and fish meal were drawn from the same lots as those
TRUE METABOLIZABLE ENERGY
1327
TABLE 3. Effect of level of inclusion and duration of excreta collection on true metabolizable energy values (kcal/g dry matter)*' Fish meal
Meat meal
Wheat
Dehydrated alfalfa
Input (g/bird)
10
20
30
10
20
30
10
20
30
10
20
30
24 hr collection Mean SEM
3.93 .07
3.81 .05
3.74 .03
2,90 .06
2.86 .06
2.86 .09
3.29 .16
3.22 .04
3.35 .08
1.41 .11
1.66 .17
2.24 .48
48 hr collection Mean SEM
3.94 .16
3.82 .06
3.72 .04
2.81 .13
2.73 .08
2.72 .07
3.27 .12
3.15 .06
3.21 .04
1.29 .18
1.16 .04
1.46 .11
Data from Experiment 1.
cal explanation for this. The trend was not apparent in the fish meal data and in an earlier investigation (Sibbald, 1977a) there were no significant differences associated with input over the range of 10 to 100 g of feed per bird. The TME values of the alfalfa, based on a 24 hr excreta collection period, increased markedly with the level of input suggesting that feed residues cleared the alimentary canal at a slower rate (%) as the input increased. The data based on the 48 hr collection were variable and the trend with input seemed to have disappeared. Thus differences in rate of passage seemed to be implicated in the earlier trend. It is interesting to note that among the meat meal, fish meal, and alfalfa data the differences between 24 and 48 hr values increased with level of feed input. This suggests that rate of clearance of residues (%) was inversely related to input levels. Although reduction of input levels may have decreased the time required for residues to clear the alimentary canal it was usually accompanied by an increase in the standard errors of the means. This was not unexpected (Sibbald, 1977a). The 24 hr alfalfa data were exceptions as variability increased with input perhaps reflecting increasing variation among residue retention times. The results of the statistical analysis are summarized in Table 4. The TME values of the feedingstuffs were each different one from the other (P<.01). There were several other significant differences but the most important was the three-way interaction (Hx Bx F) which indicates that data based on a 24 hr, but not a 48 hr, excreta collection period for alfalfa, but not for wheat, meat meal, and fish meal, were
smaller when the input was 10 g as compared to 20 and 30 g. The small differences associated with duration of the excreta collection period and levels of input of wheat, meat meal and fish meal were not statistically significant (P>.05). It is concluded that in the TME assay the excreta collection period should vary according to the feedingstuffs being evaluated. Wheat requires no more than 24 hr. Meat meal and fish meal may require a slightly longer period while dehydrated alfalfa requires a substantially longer period. Reducing the level of feed input reduced the time required for residues to clear the alimentary canal but the gain in time was comparatively small and was accompanied by increased variability among the data. The mean TME values of the basal diet fed in the second experiment, based on 24 and 48 hr excreta collections, were 3.72 ± .02 and 3.72 ± .02. The lack of difference indicates that the residues of the diet cleared the alimentary canal within 24 hr of administration. The mean TME values of the dehydrated alfalfa, meat meal, and fish meal are displayed in Table 5. Extension of the excreta collection periods from 24 to 48 hr consistently reduced the TME values. The effect was largest for the alfalfa and least for the fish meal. The 24 hr values for the alfalfa decreased as the amount of basal relative to alfalfa increased. This suggests that the basal diet encouraged more rapid passage of alfalfa residues but it is possible that the effect was due to lower alfalfa inputs as observed in the first experiment. After 48 hr of excreta collection the alfalfa and meat meal values were remarkably uniform indicating that the presence of the basal diet
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 24, 2015
Each value is the mean of 7 determinations.
SIBBALD
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TABLE 4. Analysis of the true metabolizable energy data of Experiment 1 Degrees of freedom
Source of variation Feedingstuffs (A) Alfalfa vs. meat + fish + wheat (B) Meat vs. fish + wheat (C) Fish vs. wheat (D) Levels of input (E) lOw. 20+ 30g(F)
Mean squares 39.774078*'
3 1 1 1 2 1 1 6 72 1 3 1 1 1 2 1 1 6 1 72
20OT. 30g(G)
14.630628** 7.064400** .168331 .000058 .336604 .360429 .198548 1.153371** .456514** 1.292203** .043740 .033600 .161764** .264096**
.059432 .075167* .404000* * .031007
*P<.05. **P<.01.
did n o t affect their utilization. This s u p p o r t s t h e finding t h a t TME values are additive (Sibbald, 1 9 7 7 c ) . T h e TME values for fish meal fed as 1:2 m i x t u r e with t h e basal diet were relatively large and t e n d e d t o be m o r e variable t h a n t h e o t h e r fish meal values. T h e r e is n o a p p a r e n t explanation for this finding. T h e split p l o t analysis d e m o n s t r a t e d t h a t m o s t of t h e variation was a t t r i b u t a b l e t o differ-
ences b e t w e e n t h e feedingstuffs ( P < . 0 1 ) . T h e d u r a t i o n of t h e excreta collection period also had a significant ( P < . 0 1 ) effect. Partitioning t h e variance a m o n g individual degrees of freed o m confirmed t h a t t h e d u r a t i o n of collection effect was greater for the alfalfa t h a n for t h e meat and fish meals ( P < . 0 1 ) and t h a t t h e effect o n m e a t meal was greater t h a n t h a t o n fish meal ( P < . 0 1 ) . T h u s , as in t h e first e x p e r i m e n t , t h e
TABLE 5. Effect of dilution with a basal diet and duration of excreta collection on true metabolizable energy values (kcal/g dry matter)*?0 Dehydrated Alfalfa
Meal meal
Fish meal
Input (g/bird) c
30
20
10
30
20
10
30
20
10
24 hr collection Mean SEM
1.52 .12
1.46 .09
1.40 .07
2.92 .04
2.94 .07
2.95 .06
3.27 .04
3.29 .05
3.56 .08
48 hr collection Mean SEM
1.21 .06
1.19 .09
1.25 .06
2.79 .03
2.74 .06
2.78 .07
3.17 .04
3.23 .05
3.48 .11
Each value is the mean of 8 determinations. Data from Experiment 2. c
Made to 30 g with basal diet.
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AXE Residual between birds Excreta collection periods (H) HX A HX B HX C HX D HX E HX F HX G HX AX E HX BX F Residual within birds
97.627207**
TRUE METABOLIZABLE ENERGY
ACKNOWLEDGMENTS
The author wishes to thank K. Price for suggestions regarding the statistical analysis. S. Tobin and M. Baker provided valuable technical support. The proximate analyses were con-
ducted by the Chemical and Biological Research Institute of Agriculture Canada. REFERENCES Jones, J. D., and I. R. Sibbald, 1979. The true metabolizable energy values for poultry of fractions of rapeseed (B. napus cult. Tower). Poultry Sci. 58: 385-391. Sibbald, I. R., 1976. A bioassay for true metabolizable energy in feedingstuffs. Poultry Sci. 55:303—308. Sibbald, I. R., 1977a. The effect of level of feed input on true metabolizable energy values. Poultry Sci. 56:1662-1663. Sibbald, I. R., 1977b. The true metabolizable energy values for poultry of rapeseed and of the meal and oil derived therefrom. Poultry Sci. 56:1652—1656. Sibbald, I. R., 1977c. A test of the additivity of true metabolizable energy values of feedingstuffs. Poultry Sci. 56:363-366. Sibbald, I. R., 1978a. The effect of the duration of the time interval between assays on true metabolizable energy values measured with adult roosters. Poultry Sci. 57:455-460. Sibbald, I. R., 1978b. The true metabolizable energy values of mixtures of tallow with either soybean oil or lard. Poultry Sci. 57:473-477. Sibbald, I. R., 1979a. A bioassay for available amino acids and true metabolizable energy in feedingstuffs. Poultry Sci. 58:668-673. Sibbald, I. R., 1979b. Passage of feed through the adult rooster. Poultry Sci. 58:446—459. Sibbald, I. R., 1979c. The effect of the duration of the excreta collection period on the true metabolizable energy values of feedingstuffs with slow rates of passage. Poultry Sci. (In press). Sibbald, I. R., and J. K. G. Kramer, 1977. The true metabolizable energy values of fats and fat mixtures. Poultry Sci. 56:2079-2086.
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dehydrated alfalfa had the slowest rate of passage. Meat meal residue's took more than 24 hr to clear the alimentary canal while fish meal residues were almost cleared within 24 hr. There were no significant (P>.05) differences associated with feeding the test materials in conjunction with the basal diet. In the first experiment the mean 48 hr TME values for dehydrated alfalfa, meat meal, and fish meal were 1.30, 2.75, and 3.21 kcal/g DM, respectively. These compare favorably with values of 1.22, 2.77, and 3.29 in the second experiment. In experiments of this type, where very small levels of feedingstuffs are used, the sampling procedure is important. The foregoing data suggest that variation due to sampling and experimental error were maintained within acceptable limits. The problem of slow rates of passage can be overcome by extending the excreta collection period. Reducing the feed input (Experiment 1) and dilution with a basal diet (Experiment 2) were not acceptable solutions. It is therefore important to identify those characteristics of a feedingstuff which determine its rate of passage through the alimentary canals of assay birds.
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1979 Poultry Science 58:1325-1329 INTRODUCTION The rate of passage of feed residues through the alimentary canal can be important in some bioassays. The assays for true metabolizable energy (TME) (Sibbald, 1976) and true available amino acids (Sibbald, 1979a) involve force-feeding starved birds and collecting the excreta voided during the subsequent 24 hr. However, there is evidence that the residues of some feedingstuffs take more than 24 hr to clear the alimentary canal (Sibbald, 1978a, 1979b; Jones and Sibbald, 1979). If the residues do not clear the canal within the collection period the observed TME values are too large. The problem can be overcome by extending the excreta collection period (Sibbald, 1979c) but this lengthens the time of the assay. The experiments described in this report were designed to investigate two possible procedures for ensuring complete clearance of feed residues within 24 hr of feeding. The first experiment involved feeding graded levels of feedingstuffs to determine if rate of passage was related to feed input. Sibbald (1979a) fed graded levels of a turkey diet and observed no effect of input level on TME values; however, there was no reason to suspect a slow rate of passage. The second experiment involved measuring the TME
Contribution No. 810, Animal Research Institute.
values of feedingstuffs fed alone and in combination with a diluent known to have a rate of passage of less than 24 hr. Diluents have been used in TME bioassays of rapeseed products (Sibbald, 1977b; Jones and Sibbald, 1979) and it is usual to assay fats in conjunction with a basal diet (Sibbald and Kramer, 1977; Sibbald, 1978b). MATERIALS AND METHODS Experiment 1. Four feedingstuffs were each fed at three levels to adult, Single Comb White Leghorn cockerels which had been starved for 24 hr. Seven birds were assigned to each treatment. Seven additional birds, which received no feed, served as negative controls for the measurement of metabolic plus endogenous energy excretion. The feedingstuffs, which were placed directly into the crops of the birds, were wheat, meat meal, fish meal, and dehydrated alfalfa. Their proximate compositions are presented in Table 1. The levels of input were 10, 20, and 30 g of air dry material per bird. The time of force-feeding was recorded for each bird and the excreta voided from 0 to 24 hr, and from 24 to 48 hr post-feeding was collected quantitatively. The excreta samples were frozen, freeze-dried, equilibrated with atmospheric moisture, and weighed. Samples of the feed and excreta were assayed for gross energy content with an adiabatic oxygen bomb calorimeter.
1325
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 24, 2015
ABSTRACT Adult, Leghorn cockerels were used in two bioassays designed to study the effect of 24 and 48 hr excreta collection periods on true metabolizable energy (TME) values of feedingstuffs. In the first experiment, 4 feedingstuffs were each evaluated at input levels of 10,20, and 30 g/bird. In the second assay 3 feedingstuffs were fed alone and as blends with a carrier. A reduction in TME value associated with extension of the excreta collection period was evidence that feed residues had not cleared the alimentary canal within 24 hr. Residues of wheat and of the carrier cleared the canal within 24 hr while those of fish meal were almost cleared. Residues of dehydrated alfalfa and, to a lesser extent, meat meal required a longer period. Varying input levels, and dilution with a carrier, had minor effects on clearance times. It is concluded that the duration of the excreta collection period must be adjusted according to the rate of passage of the material being assayed. Reduction in input or blending with a carrier were not satisfactory solutions to the problems of slow residue clearance.
SIBBALD
1326
TABLE 1. Proximate compositions of the feedingstuffs (% of dry matter) and gross energy content (kcal/g)
Wheat
Meat meal
Fish meal
Dehydrated alfalfa
.4.7 2.77 3.86 2.30 4.43
52.8 9.86 4.34 25.90 4,23
60.6 7.28 .54 24.56 4.37
15.9 3.40 29.10 9.10 4.44
Crude protein (N X 6.25) Ether extract Crude fiber Ash Gross energy
TABLE 2. Compositions of the feedingstuffs assayed in Experiment 2 (g)
Feedingstuff
Basal diet 3
1 2 3 4 5 6 7 8 9 10
30 0 10 20 0 10 20 0 10 20
Dehyhydrated alfalfa^
Meat meal b
Fish meal b
30 20 10 30 20 10
95% Ground wheat + 5% tallow. For composition see Table 1.
30 20 10
used in Experiment 1. The TME values of the dehydrated alfalfa, meat meal, and fish meal based on 24 and 48 hr of excreta collection were determined. When these materials were fed as mixtures their values were calculated by difference using the appropriate mean values for the basal diet. The data were subjected to an analysis of variance using a split plot design.
RESULTS AND DISCUSSION The mean TME values of Experiment 1 are displayed in Table 3. The duration of the excreta collection period had no effect upon the TME values of wheat indicating that the undigested residues cleared the alimentary canal within 24 hr. It is interesting to note that the overall mean value for the wheat (3.83 kcal/g) is similar to the value of 3.80 kcal/g obtained when wheat drawn from the same lot was assayed in an earlier experiment (Sibbald, 1979c). The TME values of meat meal and fish meal decreased slightly when the excretion collection period was extended from 24 to 48 hr suggesting that some residues had not cleared the alimentary canal within 24 hr. The differences were small and of questionable practical significance. In an earlier study of rate of passage, residues of meat meal and fish meal took longer than 24 hr to clear the alimentary canal (Sibbald, 1979b), but the findings are not directly comparable because the origins of the samples were different. The TME values of the alfalfa decreased markedly as the duration of the excreta collection period was extended demonstrating that residues remained in the alimentary canal for more than 24 hr. This confirms the observations of Sibbald (1979b,c). The 48 hr TME values of wheat and meat meal appeared to decrease slightly as the level of input increased. There is no apparent biologi-
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 24, 2015
The energy excreted per bird for the periods 0 to 24 and 0 to 48 hr post-feeding were calculated. The resulting data, together with the gross energy values of the feeds, were used to calculate TME values for each feed fed to each bird for two excreta collection periods. The TME data were subjected to an analysis of variance using a split plot deisgn. The latter was necessary because the two values obtained with each bird were not independent. Experiment 2. Ten feedingstuffs were assayed for TME content using similar procedures to those described above. Eight birds were assigned to each feedingstuff. Feed inputs were held constant at 30 g/bird. The feedingstuffs are described in Table 2. The basal diet consisted primarily of wheat which is known to clear the alimentary canal within 24 hr (Experiment 1). Fat was added to reduce dustiness and to facilitate force-feeding. The dehydrated alfalfa, meat meal, and fish meal were drawn from the same lots as those
TRUE METABOLIZABLE ENERGY
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TABLE 3. Effect of level of inclusion and duration of excreta collection on true metabolizable energy values (kcal/g dry matter)*' Fish meal
Meat meal
Wheat
Dehydrated alfalfa
Input (g/bird)
10
20
30
10
20
30
10
20
30
10
20
30
24 hr collection Mean SEM
3.93 .07
3.81 .05
3.74 .03
2,90 .06
2.86 .06
2.86 .09
3.29 .16
3.22 .04
3.35 .08
1.41 .11
1.66 .17
2.24 .48
48 hr collection Mean SEM
3.94 .16
3.82 .06
3.72 .04
2.81 .13
2.73 .08
2.72 .07
3.27 .12
3.15 .06
3.21 .04
1.29 .18
1.16 .04
1.46 .11
Data from Experiment 1.
cal explanation for this. The trend was not apparent in the fish meal data and in an earlier investigation (Sibbald, 1977a) there were no significant differences associated with input over the range of 10 to 100 g of feed per bird. The TME values of the alfalfa, based on a 24 hr excreta collection period, increased markedly with the level of input suggesting that feed residues cleared the alimentary canal at a slower rate (%) as the input increased. The data based on the 48 hr collection were variable and the trend with input seemed to have disappeared. Thus differences in rate of passage seemed to be implicated in the earlier trend. It is interesting to note that among the meat meal, fish meal, and alfalfa data the differences between 24 and 48 hr values increased with level of feed input. This suggests that rate of clearance of residues (%) was inversely related to input levels. Although reduction of input levels may have decreased the time required for residues to clear the alimentary canal it was usually accompanied by an increase in the standard errors of the means. This was not unexpected (Sibbald, 1977a). The 24 hr alfalfa data were exceptions as variability increased with input perhaps reflecting increasing variation among residue retention times. The results of the statistical analysis are summarized in Table 4. The TME values of the feedingstuffs were each different one from the other (P<.01). There were several other significant differences but the most important was the three-way interaction (Hx Bx F) which indicates that data based on a 24 hr, but not a 48 hr, excreta collection period for alfalfa, but not for wheat, meat meal, and fish meal, were
smaller when the input was 10 g as compared to 20 and 30 g. The small differences associated with duration of the excreta collection period and levels of input of wheat, meat meal and fish meal were not statistically significant (P>.05). It is concluded that in the TME assay the excreta collection period should vary according to the feedingstuffs being evaluated. Wheat requires no more than 24 hr. Meat meal and fish meal may require a slightly longer period while dehydrated alfalfa requires a substantially longer period. Reducing the level of feed input reduced the time required for residues to clear the alimentary canal but the gain in time was comparatively small and was accompanied by increased variability among the data. The mean TME values of the basal diet fed in the second experiment, based on 24 and 48 hr excreta collections, were 3.72 ± .02 and 3.72 ± .02. The lack of difference indicates that the residues of the diet cleared the alimentary canal within 24 hr of administration. The mean TME values of the dehydrated alfalfa, meat meal, and fish meal are displayed in Table 5. Extension of the excreta collection periods from 24 to 48 hr consistently reduced the TME values. The effect was largest for the alfalfa and least for the fish meal. The 24 hr values for the alfalfa decreased as the amount of basal relative to alfalfa increased. This suggests that the basal diet encouraged more rapid passage of alfalfa residues but it is possible that the effect was due to lower alfalfa inputs as observed in the first experiment. After 48 hr of excreta collection the alfalfa and meat meal values were remarkably uniform indicating that the presence of the basal diet
Downloaded from http://ps.oxfordjournals.org/ at University of North Dakota on May 24, 2015
Each value is the mean of 7 determinations.
SIBBALD
1328
TABLE 4. Analysis of the true metabolizable energy data of Experiment 1 Degrees of freedom
Source of variation Feedingstuffs (A) Alfalfa vs. meat + fish + wheat (B) Meat vs. fish + wheat (C) Fish vs. wheat (D) Levels of input (E) lOw. 20+ 30g(F)
Mean squares 39.774078*'
3 1 1 1 2 1 1 6 72 1 3 1 1 1 2 1 1 6 1 72
20OT. 30g(G)
14.630628** 7.064400** .168331 .000058 .336604 .360429 .198548 1.153371** .456514** 1.292203** .043740 .033600 .161764** .264096**
.059432 .075167* .404000* * .031007
*P<.05. **P<.01.
did n o t affect their utilization. This s u p p o r t s t h e finding t h a t TME values are additive (Sibbald, 1 9 7 7 c ) . T h e TME values for fish meal fed as 1:2 m i x t u r e with t h e basal diet were relatively large and t e n d e d t o be m o r e variable t h a n t h e o t h e r fish meal values. T h e r e is n o a p p a r e n t explanation for this finding. T h e split p l o t analysis d e m o n s t r a t e d t h a t m o s t of t h e variation was a t t r i b u t a b l e t o differ-
ences b e t w e e n t h e feedingstuffs ( P < . 0 1 ) . T h e d u r a t i o n of t h e excreta collection period also had a significant ( P < . 0 1 ) effect. Partitioning t h e variance a m o n g individual degrees of freed o m confirmed t h a t t h e d u r a t i o n of collection effect was greater for the alfalfa t h a n for t h e meat and fish meals ( P < . 0 1 ) and t h a t t h e effect o n m e a t meal was greater t h a n t h a t o n fish meal ( P < . 0 1 ) . T h u s , as in t h e first e x p e r i m e n t , t h e
TABLE 5. Effect of dilution with a basal diet and duration of excreta collection on true metabolizable energy values (kcal/g dry matter)*?0 Dehydrated Alfalfa
Meal meal
Fish meal
Input (g/bird) c
30
20
10
30
20
10
30
20
10
24 hr collection Mean SEM
1.52 .12
1.46 .09
1.40 .07
2.92 .04
2.94 .07
2.95 .06
3.27 .04
3.29 .05
3.56 .08
48 hr collection Mean SEM
1.21 .06
1.19 .09
1.25 .06
2.79 .03
2.74 .06
2.78 .07
3.17 .04
3.23 .05
3.48 .11
Each value is the mean of 8 determinations. Data from Experiment 2. c
Made to 30 g with basal diet.
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AXE Residual between birds Excreta collection periods (H) HX A HX B HX C HX D HX E HX F HX G HX AX E HX BX F Residual within birds
97.627207**
TRUE METABOLIZABLE ENERGY
ACKNOWLEDGMENTS
The author wishes to thank K. Price for suggestions regarding the statistical analysis. S. Tobin and M. Baker provided valuable technical support. The proximate analyses were con-
ducted by the Chemical and Biological Research Institute of Agriculture Canada. REFERENCES Jones, J. D., and I. R. Sibbald, 1979. The true metabolizable energy values for poultry of fractions of rapeseed (B. napus cult. Tower). Poultry Sci. 58: 385-391. Sibbald, I. R., 1976. A bioassay for true metabolizable energy in feedingstuffs. Poultry Sci. 55:303—308. Sibbald, I. R., 1977a. The effect of level of feed input on true metabolizable energy values. Poultry Sci. 56:1662-1663. Sibbald, I. R., 1977b. The true metabolizable energy values for poultry of rapeseed and of the meal and oil derived therefrom. Poultry Sci. 56:1652—1656. Sibbald, I. R., 1977c. A test of the additivity of true metabolizable energy values of feedingstuffs. Poultry Sci. 56:363-366. Sibbald, I. R., 1978a. The effect of the duration of the time interval between assays on true metabolizable energy values measured with adult roosters. Poultry Sci. 57:455-460. Sibbald, I. R., 1978b. The true metabolizable energy values of mixtures of tallow with either soybean oil or lard. Poultry Sci. 57:473-477. Sibbald, I. R., 1979a. A bioassay for available amino acids and true metabolizable energy in feedingstuffs. Poultry Sci. 58:668-673. Sibbald, I. R., 1979b. Passage of feed through the adult rooster. Poultry Sci. 58:446—459. Sibbald, I. R., 1979c. The effect of the duration of the excreta collection period on the true metabolizable energy values of feedingstuffs with slow rates of passage. Poultry Sci. (In press). Sibbald, I. R., and J. K. G. Kramer, 1977. The true metabolizable energy values of fats and fat mixtures. Poultry Sci. 56:2079-2086.
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dehydrated alfalfa had the slowest rate of passage. Meat meal residue's took more than 24 hr to clear the alimentary canal while fish meal residues were almost cleared within 24 hr. There were no significant (P>.05) differences associated with feeding the test materials in conjunction with the basal diet. In the first experiment the mean 48 hr TME values for dehydrated alfalfa, meat meal, and fish meal were 1.30, 2.75, and 3.21 kcal/g DM, respectively. These compare favorably with values of 1.22, 2.77, and 3.29 in the second experiment. In experiments of this type, where very small levels of feedingstuffs are used, the sampling procedure is important. The foregoing data suggest that variation due to sampling and experimental error were maintained within acceptable limits. The problem of slow rates of passage can be overcome by extending the excreta collection period. Reducing the feed input (Experiment 1) and dilution with a basal diet (Experiment 2) were not acceptable solutions. It is therefore important to identify those characteristics of a feedingstuff which determine its rate of passage through the alimentary canals of assay birds.
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