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Research Note: A Comparison of Methods to Determine the Metabolizable Energy of Feather Meal1
Research Note: A Comparison of Methods to Determine the Metabolizable Energy of Feather Meal1 G. M. PESTI2 and N. M. DALE Division of Poultry Science, University of Georgia, Athens, Georgia 30602 and D. J. FARRELL Department of Biochemistry, Microbiology, and Nutrition, University of New England, Armiaale, New South Wales 2351 Australia
ABSTRACT Metabolizable energy values of a feather meal sample were compared using four different assay techniques. One variation of the classical chick assay (substitution for basal diet, full-fed chicks, 0 to 14 days of age, chromic oxide indicator) gave 2.34 ± .08 kcal ME„/g dry matter when substituted into the reference diet at 400 g/kg, and 2.83 ± .12 kcal/g at 200 g/kg. A second MEn variation (substitution for basal diet, full-fed chicks, 7 to 14 days of age, total excreta collection) gave a value of 2.77 ± .04 kcal/g when substituted into the reference diet at 400 g/kg. Values from Sibbald's (1986) TME„ and Farrell's (1978) AMEn assays using adult cockerels were 3.34 ± .09 and 3.42 ± .10 kcal/g, respectively. Values derived from the two rapid cockerel assays were essentially the same but higher than those from the classical type of assay with ad libitum-fed chicks. (Key words: feather meal, assay methods, metabolizable energy, TME„, AME„) 1989 Poultry Science 68:443-446 INTRODUCTION
Numerous comparisons have been made of feed values using true (TME) and apparent (AME) metabolizable energy assays, largely without correction to zero nitrogen balance (Sibbald and Price, 1977; Halloran and Sibbald, 1979; Halloran, 1980; Mateos and Sell, 1980; Ranaweera and Nano, 1981; Schang and Hamilton, 1982; Storey and Allen, 1982). The TME values are often biased, being functions of the metabolizable energy and N contents of the feed (Dale and Fuller, 1984). Some authors have regarded their assays to be TME, but have used ad libitum feeding or have trained their birds to consume large amounts of feed in a short period of time (Kussaibati et al., 1982; Jonsson and McNab, 1983; du Preez et al., 1984). In other comparisons of TME and AME, the AME assay was with fasted cockerels given the test ingredient alone and not substituted into the diet as in the classical 'Supported by State and Hatch funds allocated to the Georgia Agricultural Experiment Stations of the University of Georgia. 'To whom correspondence should be addressed.
chick assays (Sibbald, 1975; Yamazaki and ZiYi, 1982; Storey and Allen, 1982). Sibbald (1987) concluded: "TME,, and AMEn values should be similar, providing that the birds in AMEn assays maintain their feed intakes above the maintenance requirement for energy". Few direct comparisons of TME,, and AME„ of the same ingredients have been published. Mollah et al. (1983) compared the metabolizable energy of several wheat cultivars and found TME,, values to be 17 to 26% greater than AMEn values with young broiler chickens, and 5 to 9% greater with mature cockerels. In contrast, Kussaibati et al. (1982) found the AMEn or" fats t 0 be greater than the corresponding TMEn with ad libitum-fed chicks, but lower with cockerels. Sibbald (1987) pointed out that feather meal seems to give very dissimilar AMEn and TMEn values, based on comparisons of feed composition table values (National Research Council, NRC, 1984 vs. Sibbald, 1986). The assays reported here were conducted to compare metabolizable energy values obtained from the same sample of feather meal using classical chick methods, a rapid AMEn method, and the TMEn method.
443
Downloaded from http://ps.oxfordjournals.org/ at Univ of Iowa-Law Library on May 28, 2015
(Received for publication May 9, 1988)
444
PESTI ET AL. TABLE 1. Metabolizable energy of feather meal determined by four different assay methods and reported in ingredient composition tables
Method
Laboratory
1
n
Level
2
(g/kg) 200 400 400
ME,3
Feed consumption
kcal/g
kJ/g
(g/bird) 332 ± 9 281 ± 7 165 ± 18
2.83 ± .12 2.34 ± .08 2.77 ± .04
11.84 9.79 11.60 13.98 13.89
UGA UGA UNE
8 g 3
TMEn
UGA
16 16
1,000
30
AME„ UNE 5 Ingredient composition tables National Research Council, 19g4 Sibbald, 19866
400
90
3.34 ± .09 3.32 ± .05 3.42 ± .10 2.54 3.42 ± .05
± ± ± ± ±
.50 .33 .15 .21 .21
14.30 ± .40 10.62 14.29 ± .21
'UGA = University of Georgia; UNE = University of New England. Substitution of feather meal into each reference diet. 'x ± SE (dry matter basis). *Chicks fed the reference diet consumed 351 ± 9 g. 5 Chicks fed the reference diet consumed 182 ± 4 g. 'Mean of 15 reported values.
MATERIALS AND METHODS
A sample of feather meal was obtained from a producer in the mid-Western United States. Each kilogram contained 96 g moisture, 799 g crude protein, 76 g ether extract, 8.0 g crude fiber, 33 g ash, 6.2 g methionine, 41.0 g cystine, 24.7 g lysine, 56.1 g arginine, and 7.9 g tryptophan (see Pesti et al., 1986, for methods). The classical chick assays were conducted in each of two countries using the methods that each group commonly used. In the United States, at the University of Georgia (UGA), the feather meal was included in a reference diet at either 200 g/kg or 400 g/kg of dry weight at the expense of the entire reference diet. The reference and test diets each contained 3.0 g chromic oxide/kg. The reference and test diets were each fed from hatching to 14 days of age to eight pens of 10 chicks each. The UGA reference diet contained 542 g corn, 372 g dehulled soybean meal, 53 g poultry oil, 18.6 g defluorinated phosphate, 5.1 g limestone, 7.5 g vitamin and mineral premixes, and 2.1 g DL-methionine/kg. Excreta were collected when the chicks were 11 to 14 days of age (Pesti et al., 1986). In Australia, at the University of New England (UNE), only one level of dietary inclusion was fed (400 gA;g of dry weight at the expense of the entire reference diet) to three groups each
of three cross-bred male chicks. All chicks were fed a proprietary diet for 7 days after hatching. They were then fed a reference or test diet for an additional 7 days. The UNE reference diet contained 350 g corn, 500 g dehulled soybean meal, 87 g meat and bone meal, 50 g tallow, 5 g vitamin and mineral premix, 3 g DL-methionine, and 5 g salt/kg. Feed intake was recorded and excreta were collected quantitatively for the last 4 days. For the rapid AME„ method (Farrell, 1978), which was conducted at UNE, mature crossbred cockerels trained to consume their daily feed in 1 h were fasted for 32 h. Five cockerels each were then offered 90 g of a reference or test (400 g/kg feather meal) diet for 1 h. Excreta were collected quantitatively for the next 42 h. The TMEn was determined at the UGA with 16 cockerels fasted for 24 h, by placing 20 g of feather meal in the crops onehalf the birds, followed by a 36-h quantitative excreta collection. This procedure was repeated with an additional 16 birds for a total of 32 birds (Pesti et al., 1988). Variances were calculated by the method of Pesti and Ware (1986). RESULTS AND DISCUSSION
Results from the classical chick assays gave lower MEn values for feather meal than either
Downloaded from http://ps.oxfordjournals.org/ at Univ of Iowa-Law Library on May 28, 2015
Classical* Classical* Classical5
445
RESEARCH NOTE
ACKNOWLEDGMENTS
The authors gratefully acknowledge the
excellent technical assistance of Evan Thomson and Diana Fuller. REFERENCES Dale, N., 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. de 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 evaluation metabolizable energy. World's Poult. Sci. J. 40:121-130. Farrell, D. J., 1978. Rapid determination of metabolisable energy of foods using cockerels. Br. Poult. Sci. 19:303-308. Halloran, H. R., 1980. Comparison of metabolizable energy methods on identical ingredient samples. Poultry Sci. 59:1552-1553. Halloran, H. R„ and I. R. Sibbald, 1979. Metabolizable energy values of fats measured by several procedures. Poultry Sci. 58:1299-1307. Johnson, R. J., 1987. Metabolizable energy systems for broiler chickens. Pages 127-133 in: Proc. 7th Ann. Aust. Poult. Feed Conv., Sydney, Australia. Jonsson, G., and J. M. McNab, 1983. A comparison of methods for estimating the metabolisable energy of a sample of grass meal. Br. Poult. Sci. 24:349-359. Kussaibati, R., J. Guillaume, and B. Leclercq, 1982. The effects of age, dietary fat and bile salts, and feeding rate on apparent and true metabolisable energy values in chickens. Br. Poult. Sci. 23:393-403. Lessire, M., B. Leclercq, L. Conan, and J. M. Hallouis, 1985. A methodological study of the relationship between metabolizable energy values of two meat meals and their level of inclusion in the diet. Poultry Sci. 64:1721-1728. Mateos, G. G„ and J. L. Sell, 1980. True and apparent metabolizable energy value of fat for laying hens: influence of level of use. Poultry Sci. 59:369-373. Mollah, Y., W. L. Bryden, I. R. Wallis, D. Balnave, and E. F. Annison, 1983. Studies on low metabolisable energy wheats for poultry using conventional and rapid assay procedures and the effects of processing. Br. Poult. Sci. 24:81-89. National Research Council, 1984. Nutrient Requirements of Poultry. National Academy Press, Washington, DC. Pesti, G. M., N. M. Dale, and G. O. Ware, 1988. A critique of methods of estimating the variability of metabolizable energy from assays with fasted roosters. Poultry Sci. 67:1188-1191. Pesti, G. M., L. O. Faust, H. L. Fuller, N. M. Dale, and F. H. Benoff, 1986. Nutritive value of poultry by-product meal. 1. Metabolizable energy values as influenced by method of determination and level of substitution. Poultry Sci. 65:2258-2267. Pesti, G. M., and G. O. Ware, 1986. Expressing the variability in results of metabolizable energy assays. J. Nutr. 116:1385-1389. Ranaweera, K.N.P., and W. E. Nano, 1981. True and apparent metabolizable energy of some indigenous feedingstuffs and finished feeds determined by modified rooster bioassay techniques. J. Agric. Sci. Camb. 97:403^t07. Schang, M. J., and R.M.G. Hamilton, 1982. Comparison of two direct bioassays using adult cocks and four indirect
Downloaded from http://ps.oxfordjournals.org/ at Univ of Iowa-Law Library on May 28, 2015
the TME„ or AME„ cockerel assays (Table 1). As in meat meal (Lessire et al., 1985) and poultry by-product meal (Pesti et al., 1986), the estimated MEn of feather meal is dependent on its level of inclusion in the reference diet in chick studies. The UNE classical assay with 400 g/kg feather meal gave results similar to the UGA assay with 200 g/kg. The chicks at UGA, but not UNE, were fed the test diets from 1 day of age. When the UGA excreta collection started, chicks fed 400 g/kg feather meal were considerably smaller (185 ± 4 g, x ± SE) than those fed 200 g/kg (244 ± 6 g) or the controls (263 ± 5 g) fed the reference diet. Differences in feed consumption may have been a factor in the low ME,, value at 400 g/kg (Table 1). Endogenous energy losses may not have changed in proportion to exogenous losses, thus introducing a source of error into the assay. As predicted by Sibbald (1987), TME„ and AME„ assays with cockerels gave essentially the same results (3.33 vs. 3.42 kcal/g). The reason why the chick assays gave lower results is not clear, as chick energy intakes were above those required for maintenance (although some were growing faster than others). Results of the rapid AME assay are not generally corrected to nitrogen balance, as the cockerels are near N balance for most ingredients. For this high protein meal (80.0% CP), the AME was 3.56 kcal/g dry matter (14.9 kJ/ g) and 4% greater than AME,,. Metabolizable energy values found for this sample may be compared with those found in ingredient composition tables (Table 1). Results of the classical ME assays were similar to the NRC (1984) value, averaging 2.65 kcal/g compared with 2.54 kcal/g in the tables. The results of the TME„ and AMEn cockerel assays were very close to the mean value from Sibbald's (1986) table, averaging 3.36 kcal/g compared with 3.42 kcal/g in the tables. From the results reported here, it appears that TMEn and AMEn values from assays with cockerels do give similar values, but these values are significantly higher than those from the more classical type of assays with ad libitum-fed chicks. This difference has been observed previously with other ingredients (Johnson, 1987).
446
PESTI ET AL.
methods for estimating the metabohzable energy content of different feedingstuffs. Poultry Sci. 61:1344-1353. Sibbald, I. R„ 1975. The effect of level of feed intake on metabolizable energy values measured with adult roosters. Poultry Sci. 54:1990-1997. Sibbald, I. R„ 1986. The T.M.E. system of feed evaluation: methodology, feed composition data and bibliography. Tech. Bull. 1986-4E, Res. Branch, Agriculture Canada, Ottawa, Canada. Sibbald, I. R., 1987. Getting from AME to TME. Feed Management 38(1):12, 14, and 16.
Sibbald, I. R., and K. Price, 1977. True and apparent metabolizable energy values for poultry of Canadian wheats and oats measured by bioassay and predicted from physical and chemical data. Can. J. Anim. Sci. 57:365-374. Storey, M. L., and N. K. Allen, 1982. Apparent and true metabolizable energy of feedstuffs for mature, nonlaying female Embden geese. Poultry Sci. 61:739745. Yamazaki, M, and Z. Zi-Yi, 1982. A note on the effect of temperature on true and apparent metabolisable energy values of a layer diet. Br. Poult. Sci. 23:447-450.
Downloaded from http://ps.oxfordjournals.org/ at Univ of Iowa-Law Library on May 28, 2015
ABSTRACT Metabolizable energy values of a feather meal sample were compared using four different assay techniques. One variation of the classical chick assay (substitution for basal diet, full-fed chicks, 0 to 14 days of age, chromic oxide indicator) gave 2.34 ± .08 kcal ME„/g dry matter when substituted into the reference diet at 400 g/kg, and 2.83 ± .12 kcal/g at 200 g/kg. A second MEn variation (substitution for basal diet, full-fed chicks, 7 to 14 days of age, total excreta collection) gave a value of 2.77 ± .04 kcal/g when substituted into the reference diet at 400 g/kg. Values from Sibbald's (1986) TME„ and Farrell's (1978) AMEn assays using adult cockerels were 3.34 ± .09 and 3.42 ± .10 kcal/g, respectively. Values derived from the two rapid cockerel assays were essentially the same but higher than those from the classical type of assay with ad libitum-fed chicks. (Key words: feather meal, assay methods, metabolizable energy, TME„, AME„) 1989 Poultry Science 68:443-446 INTRODUCTION
Numerous comparisons have been made of feed values using true (TME) and apparent (AME) metabolizable energy assays, largely without correction to zero nitrogen balance (Sibbald and Price, 1977; Halloran and Sibbald, 1979; Halloran, 1980; Mateos and Sell, 1980; Ranaweera and Nano, 1981; Schang and Hamilton, 1982; Storey and Allen, 1982). The TME values are often biased, being functions of the metabolizable energy and N contents of the feed (Dale and Fuller, 1984). Some authors have regarded their assays to be TME, but have used ad libitum feeding or have trained their birds to consume large amounts of feed in a short period of time (Kussaibati et al., 1982; Jonsson and McNab, 1983; du Preez et al., 1984). In other comparisons of TME and AME, the AME assay was with fasted cockerels given the test ingredient alone and not substituted into the diet as in the classical 'Supported by State and Hatch funds allocated to the Georgia Agricultural Experiment Stations of the University of Georgia. 'To whom correspondence should be addressed.
chick assays (Sibbald, 1975; Yamazaki and ZiYi, 1982; Storey and Allen, 1982). Sibbald (1987) concluded: "TME,, and AMEn values should be similar, providing that the birds in AMEn assays maintain their feed intakes above the maintenance requirement for energy". Few direct comparisons of TME,, and AME„ of the same ingredients have been published. Mollah et al. (1983) compared the metabolizable energy of several wheat cultivars and found TME,, values to be 17 to 26% greater than AMEn values with young broiler chickens, and 5 to 9% greater with mature cockerels. In contrast, Kussaibati et al. (1982) found the AMEn or" fats t 0 be greater than the corresponding TMEn with ad libitum-fed chicks, but lower with cockerels. Sibbald (1987) pointed out that feather meal seems to give very dissimilar AMEn and TMEn values, based on comparisons of feed composition table values (National Research Council, NRC, 1984 vs. Sibbald, 1986). The assays reported here were conducted to compare metabolizable energy values obtained from the same sample of feather meal using classical chick methods, a rapid AMEn method, and the TMEn method.
443
Downloaded from http://ps.oxfordjournals.org/ at Univ of Iowa-Law Library on May 28, 2015
(Received for publication May 9, 1988)
444
PESTI ET AL. TABLE 1. Metabolizable energy of feather meal determined by four different assay methods and reported in ingredient composition tables
Method
Laboratory
1
n
Level
2
(g/kg) 200 400 400
ME,3
Feed consumption
kcal/g
kJ/g
(g/bird) 332 ± 9 281 ± 7 165 ± 18
2.83 ± .12 2.34 ± .08 2.77 ± .04
11.84 9.79 11.60 13.98 13.89
UGA UGA UNE
8 g 3
TMEn
UGA
16 16
1,000
30
AME„ UNE 5 Ingredient composition tables National Research Council, 19g4 Sibbald, 19866
400
90
3.34 ± .09 3.32 ± .05 3.42 ± .10 2.54 3.42 ± .05
± ± ± ± ±
.50 .33 .15 .21 .21
14.30 ± .40 10.62 14.29 ± .21
'UGA = University of Georgia; UNE = University of New England. Substitution of feather meal into each reference diet. 'x ± SE (dry matter basis). *Chicks fed the reference diet consumed 351 ± 9 g. 5 Chicks fed the reference diet consumed 182 ± 4 g. 'Mean of 15 reported values.
MATERIALS AND METHODS
A sample of feather meal was obtained from a producer in the mid-Western United States. Each kilogram contained 96 g moisture, 799 g crude protein, 76 g ether extract, 8.0 g crude fiber, 33 g ash, 6.2 g methionine, 41.0 g cystine, 24.7 g lysine, 56.1 g arginine, and 7.9 g tryptophan (see Pesti et al., 1986, for methods). The classical chick assays were conducted in each of two countries using the methods that each group commonly used. In the United States, at the University of Georgia (UGA), the feather meal was included in a reference diet at either 200 g/kg or 400 g/kg of dry weight at the expense of the entire reference diet. The reference and test diets each contained 3.0 g chromic oxide/kg. The reference and test diets were each fed from hatching to 14 days of age to eight pens of 10 chicks each. The UGA reference diet contained 542 g corn, 372 g dehulled soybean meal, 53 g poultry oil, 18.6 g defluorinated phosphate, 5.1 g limestone, 7.5 g vitamin and mineral premixes, and 2.1 g DL-methionine/kg. Excreta were collected when the chicks were 11 to 14 days of age (Pesti et al., 1986). In Australia, at the University of New England (UNE), only one level of dietary inclusion was fed (400 gA;g of dry weight at the expense of the entire reference diet) to three groups each
of three cross-bred male chicks. All chicks were fed a proprietary diet for 7 days after hatching. They were then fed a reference or test diet for an additional 7 days. The UNE reference diet contained 350 g corn, 500 g dehulled soybean meal, 87 g meat and bone meal, 50 g tallow, 5 g vitamin and mineral premix, 3 g DL-methionine, and 5 g salt/kg. Feed intake was recorded and excreta were collected quantitatively for the last 4 days. For the rapid AME„ method (Farrell, 1978), which was conducted at UNE, mature crossbred cockerels trained to consume their daily feed in 1 h were fasted for 32 h. Five cockerels each were then offered 90 g of a reference or test (400 g/kg feather meal) diet for 1 h. Excreta were collected quantitatively for the next 42 h. The TMEn was determined at the UGA with 16 cockerels fasted for 24 h, by placing 20 g of feather meal in the crops onehalf the birds, followed by a 36-h quantitative excreta collection. This procedure was repeated with an additional 16 birds for a total of 32 birds (Pesti et al., 1988). Variances were calculated by the method of Pesti and Ware (1986). RESULTS AND DISCUSSION
Results from the classical chick assays gave lower MEn values for feather meal than either
Downloaded from http://ps.oxfordjournals.org/ at Univ of Iowa-Law Library on May 28, 2015
Classical* Classical* Classical5
445
RESEARCH NOTE
ACKNOWLEDGMENTS
The authors gratefully acknowledge the
excellent technical assistance of Evan Thomson and Diana Fuller. REFERENCES Dale, N., 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. de 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 evaluation metabolizable energy. World's Poult. Sci. J. 40:121-130. Farrell, D. J., 1978. Rapid determination of metabolisable energy of foods using cockerels. Br. Poult. Sci. 19:303-308. Halloran, H. R., 1980. Comparison of metabolizable energy methods on identical ingredient samples. Poultry Sci. 59:1552-1553. Halloran, H. R„ and I. R. Sibbald, 1979. Metabolizable energy values of fats measured by several procedures. Poultry Sci. 58:1299-1307. Johnson, R. J., 1987. Metabolizable energy systems for broiler chickens. Pages 127-133 in: Proc. 7th Ann. Aust. Poult. Feed Conv., Sydney, Australia. Jonsson, G., and J. M. McNab, 1983. A comparison of methods for estimating the metabolisable energy of a sample of grass meal. Br. Poult. Sci. 24:349-359. Kussaibati, R., J. Guillaume, and B. Leclercq, 1982. The effects of age, dietary fat and bile salts, and feeding rate on apparent and true metabolisable energy values in chickens. Br. Poult. Sci. 23:393-403. Lessire, M., B. Leclercq, L. Conan, and J. M. Hallouis, 1985. A methodological study of the relationship between metabolizable energy values of two meat meals and their level of inclusion in the diet. Poultry Sci. 64:1721-1728. Mateos, G. G„ and J. L. Sell, 1980. True and apparent metabolizable energy value of fat for laying hens: influence of level of use. Poultry Sci. 59:369-373. Mollah, Y., W. L. Bryden, I. R. Wallis, D. Balnave, and E. F. Annison, 1983. Studies on low metabolisable energy wheats for poultry using conventional and rapid assay procedures and the effects of processing. Br. Poult. Sci. 24:81-89. National Research Council, 1984. Nutrient Requirements of Poultry. National Academy Press, Washington, DC. Pesti, G. M., N. M. Dale, and G. O. Ware, 1988. A critique of methods of estimating the variability of metabolizable energy from assays with fasted roosters. Poultry Sci. 67:1188-1191. Pesti, G. M., L. O. Faust, H. L. Fuller, N. M. Dale, and F. H. Benoff, 1986. Nutritive value of poultry by-product meal. 1. Metabolizable energy values as influenced by method of determination and level of substitution. Poultry Sci. 65:2258-2267. Pesti, G. M., and G. O. Ware, 1986. Expressing the variability in results of metabolizable energy assays. J. Nutr. 116:1385-1389. Ranaweera, K.N.P., and W. E. Nano, 1981. True and apparent metabolizable energy of some indigenous feedingstuffs and finished feeds determined by modified rooster bioassay techniques. J. Agric. Sci. Camb. 97:403^t07. Schang, M. J., and R.M.G. Hamilton, 1982. Comparison of two direct bioassays using adult cocks and four indirect
Downloaded from http://ps.oxfordjournals.org/ at Univ of Iowa-Law Library on May 28, 2015
the TME„ or AME„ cockerel assays (Table 1). As in meat meal (Lessire et al., 1985) and poultry by-product meal (Pesti et al., 1986), the estimated MEn of feather meal is dependent on its level of inclusion in the reference diet in chick studies. The UNE classical assay with 400 g/kg feather meal gave results similar to the UGA assay with 200 g/kg. The chicks at UGA, but not UNE, were fed the test diets from 1 day of age. When the UGA excreta collection started, chicks fed 400 g/kg feather meal were considerably smaller (185 ± 4 g, x ± SE) than those fed 200 g/kg (244 ± 6 g) or the controls (263 ± 5 g) fed the reference diet. Differences in feed consumption may have been a factor in the low ME,, value at 400 g/kg (Table 1). Endogenous energy losses may not have changed in proportion to exogenous losses, thus introducing a source of error into the assay. As predicted by Sibbald (1987), TME„ and AME„ assays with cockerels gave essentially the same results (3.33 vs. 3.42 kcal/g). The reason why the chick assays gave lower results is not clear, as chick energy intakes were above those required for maintenance (although some were growing faster than others). Results of the rapid AME assay are not generally corrected to nitrogen balance, as the cockerels are near N balance for most ingredients. For this high protein meal (80.0% CP), the AME was 3.56 kcal/g dry matter (14.9 kJ/ g) and 4% greater than AME,,. Metabolizable energy values found for this sample may be compared with those found in ingredient composition tables (Table 1). Results of the classical ME assays were similar to the NRC (1984) value, averaging 2.65 kcal/g compared with 2.54 kcal/g in the tables. The results of the TME„ and AMEn cockerel assays were very close to the mean value from Sibbald's (1986) table, averaging 3.36 kcal/g compared with 3.42 kcal/g in the tables. From the results reported here, it appears that TMEn and AMEn values from assays with cockerels do give similar values, but these values are significantly higher than those from the more classical type of assays with ad libitum-fed chicks. This difference has been observed previously with other ingredients (Johnson, 1987).
446
PESTI ET AL.
methods for estimating the metabohzable energy content of different feedingstuffs. Poultry Sci. 61:1344-1353. Sibbald, I. R„ 1975. The effect of level of feed intake on metabolizable energy values measured with adult roosters. Poultry Sci. 54:1990-1997. Sibbald, I. R„ 1986. The T.M.E. system of feed evaluation: methodology, feed composition data and bibliography. Tech. Bull. 1986-4E, Res. Branch, Agriculture Canada, Ottawa, Canada. Sibbald, I. R., 1987. Getting from AME to TME. Feed Management 38(1):12, 14, and 16.
Sibbald, I. R., and K. Price, 1977. True and apparent metabolizable energy values for poultry of Canadian wheats and oats measured by bioassay and predicted from physical and chemical data. Can. J. Anim. Sci. 57:365-374. Storey, M. L., and N. K. Allen, 1982. Apparent and true metabolizable energy of feedstuffs for mature, nonlaying female Embden geese. Poultry Sci. 61:739745. Yamazaki, M, and Z. Zi-Yi, 1982. A note on the effect of temperature on true and apparent metabolisable energy values of a layer diet. Br. Poult. Sci. 23:447-450.
Downloaded from http://ps.oxfordjournals.org/ at Univ of Iowa-Law Library on May 28, 2015