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Repeatability of True Metabolizable Energy Versus Nitrogen Corrected True Metabolizable Energy Values1
Repeatability of True Metabolizable Energy Versus Nitrogen Corrected True Metabolizable Energy Values1 N. M. DALE2 and H. L. FULLER Poultry Science Department, University of Georgia, Athens, Georgia 30602 (Received for publication May 29, 1985)
INTRODUCTION
MATERIALS AND METHODS
In order for a system describing the energetic content of feedstuffs to be considered reliable, values obtained using the respective assay must be reproducible. A major impetus for the adoption of the metabolizable energy (ME) system in the late 1950's was the report of Hill and Anderson (1958), which demonstrated that ME values were far more reproducible than those of the productive energy system of Fraps (1946) which was widely used at the time. The true metabolizable energy (TME) system (Sibbald, 1976) has been proposed as a rapid means of evaluating the bioavailable energy content of feedstuffs. During the past several years, a number of reports (Dale and Fuller, 1980; Parsons et ah, 1982; Sibbald and Morse, 1983) have presented evidence supporting the need for a nitrogen correction in the true metabolizable energy assay. The repeatability of nitrogen corrected TME (TME n ) values has not been adequately investigated. A study was conducted to compare the intralaboratory repeatability of TME and TME n values.
Yellow corn and dehulled soybean meal (SBM) were chosen as the test ingredients in this study, as they are the two principal sources of energy in poultry diets in North America. Seven samples of yellow corn and seven of SBM were obtained from commercial channels. All were evaluated for proximate composition (AOAC, 1980). Each sample was assayed twice for TME and TME n content, using the method of Sibbald (1976) with several minor modifications as described by Dale and Fuller (1985). Single Comb White Leghorn roosters (Shaver) were used in all assays, with 10 replicates/ treatment and a 30-g level of feeding. Excreta collection periods of 30 and 48 hr were employed in the assays for corn and SBM, respectively. A period of at least 2 weeks elapsed between the two assays of any given ingredient sample. The magnitudes of the variations in TME and TME n values for the two assays of each sample were compared using the T test for a difference between independent means (Bruning and Kuntz, 1968). RESULTS
1 Supported by State and Hatch funds allocated to the Georgia Agricultural Experiment Stations of the University of Georgia. 2 Present address: Extension Poultry Science Department, University of Georgia, Athens, GA 30602.
The proximate composition of the corn and soybean meal samples assayed in this study (Table 1) indicates that all were typical of the lots of these ingredients available to the feed industry. The TME and TME n values for the individual yellow corn samples (Table 2) are in close agreement with the results of earlier assays of corn conducted at this laboratory
352
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on June 2, 2015
ABSTRACT Comparisons were made between the repeatability of true metabolizable energy (TME) and nitrogen corrected TME (TMEn) values for yellow corn and dehulled soybean meal (SBM). Seven samples of each ingredient were evaluated twice for TME and TMEn content. The mean differences between the two determined TME and TMEn values (i.e., repeatability) were 1.2 and .5%, respectively, for corn and 2.6 and 2.7% for SBM. It is concluded that both TME and TMEn values are highly reproducible. (Key words.- true metabolizable energy, nitrogen correction, corn, soybean meal, chickens) 1986 Poultry Science 65:352-354
REPRODUCIBLE VALUES IN POULTRY FEED ASSAYS
353
TABLE 1. Proximate composition of yellow com and soybean meal samples Crude protein
Ether extract
Crude fiber
Ash
Dry matter
Corn 1 2 3 4 5 6 7
7.0 7.6 9.4 8.0 8.2 8.1 9.2
3.7 3.7 3.4 3.3 3.5 3.3 4.1
2.1 2.2 2.3 2.1 2.0 2.1 2.2
1.2 1.3 1.4 1.2 1.2 1.2 1.4
86.4 86.2 87.6 86.8 86.9 85.7 87.4
Soybean meal 1 2 3 4 5 6 7
51.9 50.3 47.5 47.2 50.3 47.4 46.5
.6 .6 1.0 1.3 .9 1.2 1.1
3.0 3.0 3.7 3.0 3.3 3.9 4.5
6.3 6.1 6.7 6.3 6.2 6.1 6.2
89.6 88.6 88.2 88.5 89.6 89.2 89.3
(Dale and Fuller, 1984) and reports from Canada (Sibbald, 1983), Colombia (Pavon et al, 1983), and South Africa (du Preez et al, 1984). The mean difference between the two determined TME values for each sample (i.e., lack of repeatability) was 1.2%, compared with .5% for TME n . The observed tendency toward improved repeatability with TME n was not statistically significant (P<.05). The percent differences or lack of repeatability of both TME and TME n values for soybean meal (Table 3) were markedly higher than those observed for yellow corn. The tendency toward improved repeatability in the nitrogen corrected values noted for corn was not observed with soybean meal. The mean differences of TME values was 2.6%, vs. 2.7%
for TME n . The differences in energy content (either TME or TME n ) among the individual soybean meal samples was far greater than that observed for the yellow corn. This wider range in the energy content of soybean meal samples is consistent with previous observations at this laboratory (Dale and Fuller, 1984) and may reflect either variations in the oil extraction and meal heating procedures of different soybean processors, or possibly the use of different varieties of soybeans. DISCUSSION Both TME and TME n values were found to be highly reproducible when seven corn and
TABLE 2. True metabolizable energy (TME) and nitrogen corrected TME (TMEn) contents of yellow corn TME
TMEn Assay
Assay Sample
#1
#2
X
%'
#1
#2
X
%'
1 2 3 4 5 6 7 Average
4.00 3.98 3.96 3.96 4.05 3.97 4.03
4.04 4.04 3.96 4.04 4.08 3.94 4.13
4.02 4.01 3.96 4.00 4.07 3.96 4.08 4.01
1.0 1.5 0 2.0 .7 .8 2.5 1.2%
3.91 3.83 3.87 3.86 3.91 3.86 3.92
3.92 3.89 3.84 3.86 3.96 3.86 3.92
3.92 3.86 3.86 3.86 3.94 3.86 3.92 3.88
.3 1.6 .8 0 1.3 0 0 .5%
1
Percent difference between results of the two assays.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on June 2, 2015
Sample
354
DALE AND FULLER
TABLE 3. True metabolizable energy (TME) and nitrogen corrected TME (TME„) contents of soybean meal TME
TME n
Assay
Assay
#1
#2
X
%'
#1
#2
X
%'
1 2 3 4 5 6 7 Average
3.21 3.18 3.21 3.02 3.00 2.98 2.87
3.09 3.33 3.16 3.07 2.95 2.95 2.99
3.15 3.26 3.19 3.05 2.98 2.97 2.93 3.08
3.8 4.6 1.6 1.6 1.7 1.0 4.1 2.6
2.78 2.80 2.73 2.78 2.77 2.76 2.61
2.81 2.97 2.82 2.78 2.79 2.65 2.71
2.80 2.89 2.78 2.78 2.78 2.71 2.66 2.77
1.1 5.9 3.2 0 .7 4.1 3.8 2.7
1
Percent difference between results of the two assays.
seven soybean meal samples were each assayed t w i c e at t h e same l a b o r a t o r y . While t h e nitrogen correction t e n d e d t o improve t h e repeatability of values for corn, t h e difference was n o t statistically significant. No differences in repeatability were observed b e t w e e n TME and T M E n assays of soybean meal. T o t h e k n o w l e d g e of t h e a u t h o r s , repeatability studies with this n u m b e r of samples have y e t to be c o n d u c t e d using t h e traditional metabolizable energy assay (Hill et al, 1 9 6 0 ) . T h e magnitude of t h e nitrogen corrections in this s t u d y was a p p r o x i m a t e l y three t i m e s greater for soybean meal t h a n for corn ( 1 0 . 6 vs. 3.0%, respectively). This is in agreement w i t h a previous r e p o r t from this l a b o r a t o r y (Dale and Fuller, 1 9 8 4 ) , in which a positive correlation was noted b e t w e e n t h e m a g n i t u d e of nitrogen correction and t h e percent protein of t h e feedstuff. It is n o t clear w h y b o t h TME and T M E n values are less repeatable for soybean meal t h a n for corn; however, this m a y b e a consequence of the longer excreta collection period used in assays of SBM ( 4 8 hr, vs. 30 hr for corn). When such e x t e n d e d collection periods are e m p l o y e d , t h e p r o p o r t i o n of e n d o g e n o u s t o e x o g e n o u s excreta energy increases. As t h e final correction for e n d o g e n o u s e x c r e t i o n is only an estimate of t h e actual e n d o g e n o u s loss of fed birds, t h e possibility of p o o r e r repeatability w o u l d increase with e x t e n d e d collection periods.
REFERENCES Association of Official Analytical Chemists, 1980. Official Methods of Analysis. 13th ed. Assoc. Offic. Anal. Chem., Washington, DC. Bruning, J. L., and B. L. Kuntz, 1968. Computational
Handbook of Statistics. Scott, Foresman and Co., Glenview, IL. Dale, N. M., and H. L. Fuller, 1980. Endogenous energy losses of fed versus fasted roosters. Poultry Sci. 6 1 : 8 9 8 - 9 0 1 . Dale, N. M., and H. L. Fuller, 1984. Correlation of protein content of feedstuffs with the magnitude of nitrogen correction in true metabolizable energy determinations. Poultry Sci. 63:1008— 1012. Dale, N. M., and H. L. Fuller, 1985. Freeze drying versus oven drying of excreta in true metabolizable energy, nitrogen corrected true metabolizable energy, and true amino acid availability bioassays. Poultry Sci. 64:362—365. du Preez, J. J., A. Du P. Minnaar, and J. S. Duckitt, 1984. An alternative approach to a compulsive change from conventional to rapid methods of evaluating metabolizable energy. World's Poult. Sci. J. 40:121-130. Fraps, G. S., 1946. Composition and productive energy of poultry feeds and rations. Bull. Tex. Agric. Exp. Stn. #678. Hill, F. W., and D. L. Anderson, 1958. Comparison of metabolizable energy and productive energy determinations with growing chicks. J. Nutr. 64:587-603. Hill, F. W., D. L. Anderson, R. Renner, and L. B. Carew, 1960. Studies of the metabolizable energy of grain and grain products for chickens. Poultry Sci. 39:573-593. Parsons, C. M., L. M. Potter, and B. A. Bliss, 1982. True metabolizable energy corrected to nitrogen equilibrium. Poultry Sci. 61:2241-2246. Pavon, L. G., H. Alvarez, and G. Afanader, 1983. Energia metabolizable de algunas materias primas utilizadas en la alimentacion de aves en el Ecuador. Revista del Institute) Colombiano Agropecuario 28:419-424. Sibbald, I. R., 1976. A bioassay for true metabolizable energy of feedingstuffs. Poultry Sci. 55:303 — 308. Sibbald, 1. R., 1983. The T.M.E. System of Feed Evaluation. Agriculture Canada, Ottawa. Sibbald, I. R., and P. M. Morse, 1983. Provision of supplemental feed and the application of a nitrogen correction in bioassays for true metabolizable energy. Poultry Sci. 62:1587-1605.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on June 2, 2015
Sample
INTRODUCTION
MATERIALS AND METHODS
In order for a system describing the energetic content of feedstuffs to be considered reliable, values obtained using the respective assay must be reproducible. A major impetus for the adoption of the metabolizable energy (ME) system in the late 1950's was the report of Hill and Anderson (1958), which demonstrated that ME values were far more reproducible than those of the productive energy system of Fraps (1946) which was widely used at the time. The true metabolizable energy (TME) system (Sibbald, 1976) has been proposed as a rapid means of evaluating the bioavailable energy content of feedstuffs. During the past several years, a number of reports (Dale and Fuller, 1980; Parsons et ah, 1982; Sibbald and Morse, 1983) have presented evidence supporting the need for a nitrogen correction in the true metabolizable energy assay. The repeatability of nitrogen corrected TME (TME n ) values has not been adequately investigated. A study was conducted to compare the intralaboratory repeatability of TME and TME n values.
Yellow corn and dehulled soybean meal (SBM) were chosen as the test ingredients in this study, as they are the two principal sources of energy in poultry diets in North America. Seven samples of yellow corn and seven of SBM were obtained from commercial channels. All were evaluated for proximate composition (AOAC, 1980). Each sample was assayed twice for TME and TME n content, using the method of Sibbald (1976) with several minor modifications as described by Dale and Fuller (1985). Single Comb White Leghorn roosters (Shaver) were used in all assays, with 10 replicates/ treatment and a 30-g level of feeding. Excreta collection periods of 30 and 48 hr were employed in the assays for corn and SBM, respectively. A period of at least 2 weeks elapsed between the two assays of any given ingredient sample. The magnitudes of the variations in TME and TME n values for the two assays of each sample were compared using the T test for a difference between independent means (Bruning and Kuntz, 1968). RESULTS
1 Supported by State and Hatch funds allocated to the Georgia Agricultural Experiment Stations of the University of Georgia. 2 Present address: Extension Poultry Science Department, University of Georgia, Athens, GA 30602.
The proximate composition of the corn and soybean meal samples assayed in this study (Table 1) indicates that all were typical of the lots of these ingredients available to the feed industry. The TME and TME n values for the individual yellow corn samples (Table 2) are in close agreement with the results of earlier assays of corn conducted at this laboratory
352
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on June 2, 2015
ABSTRACT Comparisons were made between the repeatability of true metabolizable energy (TME) and nitrogen corrected TME (TMEn) values for yellow corn and dehulled soybean meal (SBM). Seven samples of each ingredient were evaluated twice for TME and TMEn content. The mean differences between the two determined TME and TMEn values (i.e., repeatability) were 1.2 and .5%, respectively, for corn and 2.6 and 2.7% for SBM. It is concluded that both TME and TMEn values are highly reproducible. (Key words.- true metabolizable energy, nitrogen correction, corn, soybean meal, chickens) 1986 Poultry Science 65:352-354
REPRODUCIBLE VALUES IN POULTRY FEED ASSAYS
353
TABLE 1. Proximate composition of yellow com and soybean meal samples Crude protein
Ether extract
Crude fiber
Ash
Dry matter
Corn 1 2 3 4 5 6 7
7.0 7.6 9.4 8.0 8.2 8.1 9.2
3.7 3.7 3.4 3.3 3.5 3.3 4.1
2.1 2.2 2.3 2.1 2.0 2.1 2.2
1.2 1.3 1.4 1.2 1.2 1.2 1.4
86.4 86.2 87.6 86.8 86.9 85.7 87.4
Soybean meal 1 2 3 4 5 6 7
51.9 50.3 47.5 47.2 50.3 47.4 46.5
.6 .6 1.0 1.3 .9 1.2 1.1
3.0 3.0 3.7 3.0 3.3 3.9 4.5
6.3 6.1 6.7 6.3 6.2 6.1 6.2
89.6 88.6 88.2 88.5 89.6 89.2 89.3
(Dale and Fuller, 1984) and reports from Canada (Sibbald, 1983), Colombia (Pavon et al, 1983), and South Africa (du Preez et al, 1984). The mean difference between the two determined TME values for each sample (i.e., lack of repeatability) was 1.2%, compared with .5% for TME n . The observed tendency toward improved repeatability with TME n was not statistically significant (P<.05). The percent differences or lack of repeatability of both TME and TME n values for soybean meal (Table 3) were markedly higher than those observed for yellow corn. The tendency toward improved repeatability in the nitrogen corrected values noted for corn was not observed with soybean meal. The mean differences of TME values was 2.6%, vs. 2.7%
for TME n . The differences in energy content (either TME or TME n ) among the individual soybean meal samples was far greater than that observed for the yellow corn. This wider range in the energy content of soybean meal samples is consistent with previous observations at this laboratory (Dale and Fuller, 1984) and may reflect either variations in the oil extraction and meal heating procedures of different soybean processors, or possibly the use of different varieties of soybeans. DISCUSSION Both TME and TME n values were found to be highly reproducible when seven corn and
TABLE 2. True metabolizable energy (TME) and nitrogen corrected TME (TMEn) contents of yellow corn TME
TMEn Assay
Assay Sample
#1
#2
X
%'
#1
#2
X
%'
1 2 3 4 5 6 7 Average
4.00 3.98 3.96 3.96 4.05 3.97 4.03
4.04 4.04 3.96 4.04 4.08 3.94 4.13
4.02 4.01 3.96 4.00 4.07 3.96 4.08 4.01
1.0 1.5 0 2.0 .7 .8 2.5 1.2%
3.91 3.83 3.87 3.86 3.91 3.86 3.92
3.92 3.89 3.84 3.86 3.96 3.86 3.92
3.92 3.86 3.86 3.86 3.94 3.86 3.92 3.88
.3 1.6 .8 0 1.3 0 0 .5%
1
Percent difference between results of the two assays.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on June 2, 2015
Sample
354
DALE AND FULLER
TABLE 3. True metabolizable energy (TME) and nitrogen corrected TME (TME„) contents of soybean meal TME
TME n
Assay
Assay
#1
#2
X
%'
#1
#2
X
%'
1 2 3 4 5 6 7 Average
3.21 3.18 3.21 3.02 3.00 2.98 2.87
3.09 3.33 3.16 3.07 2.95 2.95 2.99
3.15 3.26 3.19 3.05 2.98 2.97 2.93 3.08
3.8 4.6 1.6 1.6 1.7 1.0 4.1 2.6
2.78 2.80 2.73 2.78 2.77 2.76 2.61
2.81 2.97 2.82 2.78 2.79 2.65 2.71
2.80 2.89 2.78 2.78 2.78 2.71 2.66 2.77
1.1 5.9 3.2 0 .7 4.1 3.8 2.7
1
Percent difference between results of the two assays.
seven soybean meal samples were each assayed t w i c e at t h e same l a b o r a t o r y . While t h e nitrogen correction t e n d e d t o improve t h e repeatability of values for corn, t h e difference was n o t statistically significant. No differences in repeatability were observed b e t w e e n TME and T M E n assays of soybean meal. T o t h e k n o w l e d g e of t h e a u t h o r s , repeatability studies with this n u m b e r of samples have y e t to be c o n d u c t e d using t h e traditional metabolizable energy assay (Hill et al, 1 9 6 0 ) . T h e magnitude of t h e nitrogen corrections in this s t u d y was a p p r o x i m a t e l y three t i m e s greater for soybean meal t h a n for corn ( 1 0 . 6 vs. 3.0%, respectively). This is in agreement w i t h a previous r e p o r t from this l a b o r a t o r y (Dale and Fuller, 1 9 8 4 ) , in which a positive correlation was noted b e t w e e n t h e m a g n i t u d e of nitrogen correction and t h e percent protein of t h e feedstuff. It is n o t clear w h y b o t h TME and T M E n values are less repeatable for soybean meal t h a n for corn; however, this m a y b e a consequence of the longer excreta collection period used in assays of SBM ( 4 8 hr, vs. 30 hr for corn). When such e x t e n d e d collection periods are e m p l o y e d , t h e p r o p o r t i o n of e n d o g e n o u s t o e x o g e n o u s excreta energy increases. As t h e final correction for e n d o g e n o u s e x c r e t i o n is only an estimate of t h e actual e n d o g e n o u s loss of fed birds, t h e possibility of p o o r e r repeatability w o u l d increase with e x t e n d e d collection periods.
REFERENCES Association of Official Analytical Chemists, 1980. Official Methods of Analysis. 13th ed. Assoc. Offic. Anal. Chem., Washington, DC. Bruning, J. L., and B. L. Kuntz, 1968. Computational
Handbook of Statistics. Scott, Foresman and Co., Glenview, IL. Dale, N. M., and H. L. Fuller, 1980. Endogenous energy losses of fed versus fasted roosters. Poultry Sci. 6 1 : 8 9 8 - 9 0 1 . Dale, N. M., and H. L. Fuller, 1984. Correlation of protein content of feedstuffs with the magnitude of nitrogen correction in true metabolizable energy determinations. Poultry Sci. 63:1008— 1012. Dale, N. M., and H. L. Fuller, 1985. Freeze drying versus oven drying of excreta in true metabolizable energy, nitrogen corrected true metabolizable energy, and true amino acid availability bioassays. Poultry Sci. 64:362—365. du Preez, J. J., A. Du P. Minnaar, and J. S. Duckitt, 1984. An alternative approach to a compulsive change from conventional to rapid methods of evaluating metabolizable energy. World's Poult. Sci. J. 40:121-130. Fraps, G. S., 1946. Composition and productive energy of poultry feeds and rations. Bull. Tex. Agric. Exp. Stn. #678. Hill, F. W., and D. L. Anderson, 1958. Comparison of metabolizable energy and productive energy determinations with growing chicks. J. Nutr. 64:587-603. Hill, F. W., D. L. Anderson, R. Renner, and L. B. Carew, 1960. Studies of the metabolizable energy of grain and grain products for chickens. Poultry Sci. 39:573-593. Parsons, C. M., L. M. Potter, and B. A. Bliss, 1982. True metabolizable energy corrected to nitrogen equilibrium. Poultry Sci. 61:2241-2246. Pavon, L. G., H. Alvarez, and G. Afanader, 1983. Energia metabolizable de algunas materias primas utilizadas en la alimentacion de aves en el Ecuador. Revista del Institute) Colombiano Agropecuario 28:419-424. Sibbald, I. R., 1976. A bioassay for true metabolizable energy of feedingstuffs. Poultry Sci. 55:303 — 308. Sibbald, 1. R., 1983. The T.M.E. System of Feed Evaluation. Agriculture Canada, Ottawa. Sibbald, I. R., and P. M. Morse, 1983. Provision of supplemental feed and the application of a nitrogen correction in bioassays for true metabolizable energy. Poultry Sci. 62:1587-1605.
Downloaded from http://ps.oxfordjournals.org/ at Simon Fraser University on June 2, 2015
Sample