The Effect of Enzyme Predigestion on the Nutritional Quality of Prepressed Turkey Feather Meal1 G. W. Barbour,*,2 M. Werling,† A. G. Yersin,‡,3 and M. S. Lilburn*,4 *The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, Ohio 44691; †Cooper Farms, Inc. Fort Recovery, Ohio; and ‡NOVUS International, Inc., St. Louis, Missouri 63141 ABSTRACT Three experiments were conducted to determine the protein efficiency ratio (PER), pepsin digestibility, TMEn, and true amino acid availability (TAAA) of prepressed turkey feather meal (PFM), enzyme-digested PFM (EPFM), and commercial feather meal (CFM). Turkey feathers from a commercial processing plant were mechanically pressed alone or mechanically pressed, followed by treatment with a mixture of protease, lipase, and amylase prior to autoclaving. In the first study, feather meal diets containing 16, 20, or 24% CP from PFM, EPFM, or CFM were fed to starter poults for 10 d. All diets resulted in negative or negligible growth. In a second study, PFM, EPFM, and CFM were again the primary sources of CP, but dietary protein levels were increased to 20, 24, and 28% CP, and all diets contained 20% corn
and 10% soybean meal (PFMCS, EPFMCS, CFMCS), respectively, to allow for a basal level of growth. Performance and PER of the poults fed the diets with PFMCS, EPFMCS, and CFMCS were similar. The efficiency of use of the PFMCS diet was numerically lower (P ≤ 0.1) when compared with the EPFMCS and CFMCS diets. Similarly, pepsin digestibilities of EPFM and CFM were higher than PFM. The TAAA of PFM (82.1%) and EPFM (80.6%) were not significantly higher than that of CFM (71.4%); however, the availabilities of lysine, threonine, aspartate, glutamate, proline, and histidine were significantly higher. Digestion of pressed turkey feathers with an enzyme mixture prior to autoclaving could have a positive impact on its protein and amino acid nutritional values.
(Key words: poult, feather meal, enzyme, protein, amino acid) 2002 Poultry Science 81:1032–1037
INTRODUCTION In a report published by Naber et al. (1961), growth and feed conversion of 4-wk-old broiler chicks were hindered when all of the soybean meal in a corn-soybean meal diet was replaced with feather meal. Improvements in chick performance were observed when the corn-feather meal diet was supplemented with key amino acids, but the chicks still weighed less and had a higher feed conversion when compared with chicks fed diets containing soybean meal. In that report (Naber et al., 1961), the experimental feather meal was prepared by autoclaving fresh feathers for 90 min at 0.88 kg/cm2. Feather meal contains a high proportion of sulfur amino acids with a 6 to 1 ratio of cystine to methionine (Liu et al., 1989; Han and Parsons,
2002 Poultry Science Association, Inc. Received for publication September 28, 2001. Accepted for publication February 26, 2002. 1 Salaries and research support provided by state and federal funds appropriated to the Ohio Agricultural Research and Development Center, The Ohio State University. 2 Present address: Agriculture Research Institute, Animal Production Department, Tel. Amara, Bega, Lebanon. 3 Present address: HY-VAC Laboratory Eggs Company, 2147 Hwy 6, P.O. Box 285, Adel, IA, 50003. 4 To whom correspondence should be addressed:
[email protected].
1991; NRC, 1994) of which approximately 52% of the cystine is available for digestion and absorption (Baker et al.,1981). Under conditions of prolonged exposure to high pressure and temperature during experimental autoclaving or commercial processing, however, some of the cystine will be converted to the atypical sulfur amino acid lanthionine (Baker et al., 1981). Lanthionine has been reported to be absorbed by chicks, but it has also been observed that feather meal samples with high levels of lanthionine generally have decreased amino acid availability (Baker et al., 1981; Han and Parsons, 1991). In comparison with other ingredients of animal origin, amino acid digestibility in feather meal is poor (Nordheim and Coon, 1984), and any improvements in digestibility would allow for greater incorporation of feather meal into practical poultry diets. Pre-digestion of feathers with synthetic enzymes prior to processing is one possibility
Abbreviation Key: CFM = commercial feather meal; CFMCS = commercial feather meal diet containing 20% corn and 10% soybean meal; EPFM = enzyme-digested prepressed turkey feather meal; EPFMCS = enzyme-digested prepressed turkey feather meal diet containing 20% corn and 10% soybean meal; PER = protein efficiency ratio; PFM = prepressed turkey feather meal; PFMCS = prepressed turkey feather meal diet containing 20% corn and 10% soybean meal; TAAA = true amino acid availability.
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ENZYME PREDIGESTION AND FEATHER MEAL QUALITY
for increasing overall protein and amino acid digestibility. In one previous study, Papadopoulos et al. (1985) reported small improvements in amino acid availability from feathers treated with a protease enzyme prior to autoclaving. The objective of the current study was to study the effect of mixing feathers with a combination of synthetic enzymes, prior to autoclaving, on the nutritional value of an experimental feather meal and to compare this with commercial feather meal (CFM) when fed to young turkey poults. Poults were chosen for the experiment because of their increased protein and amino acid requirements relative to chicks. This procedure would allow for greater inclusion rates of test protein sources in experimental diets while staying within the deficiency range of the test species.
MATERIALS AND METHODS Experiment 1 Turkey feathers were obtained from a commercial processing plant. The experimental feather meals were prepared first by mechanically pressing the raw feathers followed by grinding in a heavy-duty grinder. The ground feathers were mixed 1:1 (wt:wt) with a solution containing a 0.25% enzyme mixture (EPFM) or solution alone (PFM). The enzyme cocktail contained a proprietary mixture5 of protease, lipase, and amylase. The feathers were mixed in a high-speed mixer for 20 min at 50 C and subsequently autoclaved at 125 C and 1.76 kg/cm2 for 15 min. The final, autoclaved materials were dried for 1 h at 50 C. The two experimental feather meals were subsequently compared with a CFM.6 An initial study was conducted to determine, in vivo, the protein quality of the three feather meal sources. Each of the feather meals was the sole source of dietary CP in semipurified diets containing 16, 20, or 24% CP (Table 1). Each diet was randomly allocated to two battery pens containing four or five poults, and the experimental diets were fed from 10 to 20 d of age, which resulted in nine total treatments with two replicates containing four or five poults (n = 81 total poults). An additional four replicate pens of poults (n = 4 poults per pen) were fed a Nfree diet to correct for maintenance N requirements (Table 2). The determined CP level in the N-free diet was 0.16%. Proximate analysis was conducted on samples of PFM, EPFM, and CFM as well as analysis for total amino acids and lanthionine (Table 3).7 The CP content of each test feather meal was calculated after Kjeldahl N determination. At the beginning and end of each experiment, all poults were individually weighed, and feed intake was determined. At the end of the study, all poults were killed
5
Supplied by Alltech Inc., Nicholasville, KY. Holmes Byproducts, Winesburg, OH. 7 NOVUS International, Inc., St. Louis, MO. 8 Holmes Laboratory Inc. Millersburg, OH. 6
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with CO2 gas, and the left half of the pectoralis major muscle was dissected and weighed.
Experiment 2 The diets containing 16, 20, or 24% CP feather meal in the first experiment did not result in consistent weight gains across all replicate pens so Experiment 1 was repeated with a few modifications. All of the diets in the second study were supplemented with 20% corn and 10% soybean meal to enhance feed intake and to establish a baseline level of BW gain. In addition, dietary CP levels were increased to 20, 24, and 28%. The same three feather meal sources (PFM, EPFM, and CFM) were tested (Table 4). Seven-day-old poults were randomly allocated to battery brooders with raised wire floors. Three pens were randomly allocated to each combination of feather meal source and level of CP. Five poults were allocated to two replicate pens, and the third replicate contained four poults (n = 14 poults per each of 9 total treatments). The N-free diet was again fed to four replicate pens (n = 4 poults per pen) and it contained 0.28% CP. The protein efficiency ratio (PER) and net protein ratio (NPR) were calculated for each source of feather meal and level of CP according to the equations published by Bender and Doell (1957) and Henry (1965). The rate of in vitro digestibility of PFM, EPFM, and CFM in a pepsin solution (10 mg pepsin/mL 0.1 N HCL) was also determined.8 All data were analyzed by analysis of variance using the general linear models program of SAS software (SAS Institute, 1990). The main effects were protein (feather meal) source, level of CP, and the interaction of protein source and level. When significant main effects were observed (P ≤ 0.05), Duncan’s multiple-range test was used to further test the significance of differences between treatment means at P ≤ 0.05.
Experiment 3 In this experiment, TMEn and true amino acid availability (TAAA) were determined for each of the three sources of feather meal (PFM, EPFM, CFM). The precision feeding method of Sibbald (1986) and Sibbald and Morse (1983) as modified by McNab and Blair (1988) was followed. At the beginning of the experimental period, four intact, adult leghorn cockerels were intubated and then were fed with 30 g of each feather meal source followed by 50 mL of water 24 h post-intubation. An additional set of four cockerels was intubated and then fed with 30 g of sugar to determine and correct for endogenous and metabolic energy and amino acid losses. Excreta were collected for 48 h post-intubation from the fed and fasted cockerels. Excreta were collected and pooled by cage at 24 and 48 h. All samples were dried in a forced-air draft oven at 60 to 65 C until dry. The dried excreta samples and test ingredients were analyzed for CP (Kjeldahl method) and gross energy (adiabatic bomb calorimeter). The
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BARBOUR ET AL. TABLE 1. Compositions of prepressed feather meal (PFM), enzyme-digested feather meal (EPFM), and commercial feather meal (CFM) semi-purified diets used in Experiment 1 PFM
Ingredients and analyses
16
20
EPFM 24
16
20
CFM 24
16
20
24
(%) CP, % calculated PFM EPFM CFM Solka floc Animal-vegetable fat Potassium sulfate Ground limestone Dicalcium phosphate Sodium chloride Glucose Premix1 Dietary analyses CP,2 % ME,3 kcal/kg Lysine,3 % Methionine,3 %
18.6 – – 10.8 2.4 1.5 1.0 3.4 0.18 60.1 2.0
23.2 – – 10.2 3.1 1.5 1.0 3.4 0.18 55.4 2.0
27.8 – – 8.55 3.0 1.4 1.0 3.4 0.13 52.7 2.0
– 18.0 – 11.1 2.4 1.5 1.0 3.4 0.18 60.4 2.0
– 22.4 – 9.52 2.4 1.5 1.0 3.4 0.18 57.6 2.0
– 26.9 – 7.77 2.2 1.4 1.0 3.4 0.13 55.2 2.0
– – 18.9 10.8 2.4 1.5 1.0 3.4 0.18 59.9 2.0
– – 23.5 10.1 3.1 1.5 1.2 3.3 0.16 55.1 2.0
– – 28.1 9.4 3.6 1.5 1.2 3.1 0.14 51.0 2.0
17.7 2,831 0.31 0.08
22.7 2,829 0.39 0.10
27.5 2,831 0.46 0.12
15.9 2,827 0.30 0.08
21.1 2,829 0.37 0.09
25.2 2,831 0.45 0.11
16.8 2,828 0.32 0.08
20.8 2,827 0.39 0.10
26.6 2,830 0.47 0.12
1 Vitamin and trace mineral premix contained (g/45.4 kg diet): corn, 490; choline chloride, 54.5; amprolium (25%), 22.7; selenium premix (200 mg Se/kg), 45.4; bacitracin MD, 22.7; vitamin premix, 227; and trace mineral premix, 45.4. Vitamin premix had the following per kilogram of diet: vitamin A, 8,745 IU; cholecalciferol, 3,745 IU; vitamin E, 60 IU; vitamin K (menadione sodium bisulfite), 2.91 mg; thiamin HC1, 2.2 mg; riboflavin, 6.6 mg; niacin, 99 mg; pantothenic acid, 15.4 mg; folic acid, 1.2 mg; pyridoxine, 2.2 mg; and biotin, 165 mg. Trace mineral premix contained the following per kilogram of diet: zinc oxide (72% Zn), 147 mg; manganous oxide (55% Mn), 152 mg; copper sulfate (25.2% Cu), 35 mg; ferrous sulfate monohydrate (31% Fe), 72 mg; and potassium iodide, 1.5 mg (Lilburn and Emmerson, 1993). 2 Determined value. 3 Calculated.
amino acid profile of each excreta sample was analyzed at NOVUS International, Inc.6 The TME corrected to zero nitrogen balance (TMEn) and TAAA were calculated for the three feather meal sources as described by Likuski and Dorrell (1978), Sibbald and Wolynetz (1985), and Sibbald (1986). The constant used to adjust metabolizable energy to a zero nitrogen balance status was 8,220 kcal/kg of uric acid nitrogen (Scott et al., 1982). Data were statistically analyzed for protein source effect on the TME, TMEn, and TAAA by using the general linear models program (SAS Institute, 1990). Treatment mean differences with a probability value of P ≤ 0.05 were compared using Duncan’s multiple-range test.
RESULTS The CFM was over twofold higher in crude fat and considerably higher in ash than the PFM and EPFM (Table TABLE 2. Composition of the N-free diet, Experiments 1 and 2 Ingredients
%
Glucose Animal-vegetable fat Sodium chloride Ground limestone Dicalcium phosphate Premix1 Solka floc Dietary analyses ME, kcal/kg (calculated
74.5 2.50 0.50 2.00 3.00 2.00 14.5
1
2924
Vitamin and trace mineral premix composition was similar to that reported in Table 1.
3). This result was most likely due to some inclusion of offal with the feathers prior to CFM processing. The CP levels were not too dissimilar among the different sources, but in vitro pepsin digestibility of EPFM was 18.6% higher
TABLE 3. Proximate chemical, pepsin digestibility, and amino acid composition of the prepressed, without and with enzyme, feather meal (PFM and EPFM) and commercial feather meal (CFM) Nutrient
PFM
EPFM
CFM
DM CP Crude fat Crude fiber Ash Pepsin digestibility Amino acids Methionine Cystine Lysine Arginine Tyrosine Threonine Serine Phenylalanine Aspartate Glutamate Proline Glycine Alanine Valine Isoleucine Leucine Histidine Lanthionine
93.4 87.1 2.73 0.17 3.26 56.1
(%) 94.4 89.8 2.62 0.04 2.85 74.7
95.7 85.8 5.97 0.32 5.08 64.11
0.54 6.52 1.48 6.51 2.62 4.10 10.70 4.95 6.28 9.29 9.97 7.46 4.28 7.41 4.40 7.58 0.72 0.53
0.51 6.06 1.49 6.63 2.86 4.09 10.70 5.02 6.23 9.29 10.70 7.34 4.16 7.27 4.37 7.49 0.75 4.54
0.52 4.19 1.51 6.32 2.67 3.95 10.1 4.75 6.01 8.99 10.50 7.35 4.27 7.12 4.29 7.38 0.71 4.79
1
Duplicate values were equal to 52.8 and 75.4%.
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ENZYME PREDIGESTION AND FEATHER MEAL QUALITY TABLE 4. Composition of the prepressed feather meal (PFMCS), enzyme-digested feather meal (EPFMCS), and commercial feather meal (CFMCS) diets used in Experiment 2 PFMCS
EPFMCS
Ingredients and analysis
20
24
28
20
Corn Soybean meal PFM EPFM CFM Animal-vegetable fat Sodium chloride Ground limestone Dicalcium phosphate Potassium sulfate Glucose Solka floc Premix1 Dietary analyses CP,2 % ME,3 kcal/kg
20.0 10.0 15.7 – – 4.0 0.16 1.20 3.20 1.00 32.7 10.1 2.0
20.0 10.0 20.3 – – 4.0 0.14 1.18 3.18 0.95 29.7 8.54 2.0
20.0 10.0 24.9 – – 4.0 0.12 1.19 3.08 0.95 26.7 7.05 2.0
20.0 10.0 – 15.2 – 4.0 0.16 1.20 3.20 1.00 33.0 10.2 2.0
24
CFMCS 28
20
24
28
20.0 10.0 – 24.1 – 4.0 0.12 1.19 3.08 0.95 27.2 7.33 2.0
20.0 10.0 – – 15.9 4.0 0.16 1.20 3.20 1.00 32.5 10.0 2.0
20.0 10.0 – – 20.6 4.0 0.14 1.18 3.18 0.95 29.6 8.45 2.0
20.0 10.0 – – 25.2 4.0 0.12 1.19 3.08 0.95 26.5 6.96 2.0
(%)
20.6 2,821
26.0 2,821
29.7 2,821
20.7 2,821
20.0 10.0 – 19.7 – 4.0 0.14 1.18 3.18 0.95 30.1 8.77 2.0 24.1 2,821
28.3 2,821
19.7 2,820
25.0 2,820
29.6 2,822
1
Composition of the vitamin and trace mineral premix is reported in Table 1. Determined. 3 Calculated. 2
than PFM and 10.6% higher than CFM. This latter observation might have been due to the large differences between the two replicate samples of CFM. The amino acid profiles of all three feather meals were similar although lanthionine concentrations in the EPFM and CFM were considerably higher than what has been reported by others (Baker et al., 1981; Papadopoulos et al., 1985; Han and Parsons, 1991; Moritz and Latshaw, 2001).
was a decline in the relative weight of the pectoralis major muscle in the 24 and 28% CP diets when compared with the 20% CP treatment, resulting in a significant CP effect (P ≤ 0.02). The net protein ratio (NPR) was not different among the three feather meal sources but was similar to the PER results in that the two highest CP diets resulted in lower NPR values than the 20% CP treatment (P ≤ 0.001). There were no significant interactions between source of feather meal and level of dietary protein.
Experiment 1 Feeding diets containing only feather meal as a source of protein resulted in consistent body weight losses when the diets contained only 16% CP (range of −6.6 to 11.0 g/ poult) and inconsistent small losses or gains in poults fed the 20 or 24% CP diet (data not shown).
Experiment 2 The addition of baseline levels of corn and soybean meal and increases in dietary CP improved consumption and increased BW gain in this study. The source of feather meal had no significant effects on poult growth (Table 5), although the EPFM and CFM diets, both containing 20% corn and 10% soybean meal (EPFMCS and CFMCS, respectively), did result in numerically higher gains, particularly at the 24 and 28% CP. The small gains in BW coupled with no significant differences in intake resulted in improved feed efficiency (P ≤ 0.09) in the latter two feather meal sources compared with the PFMCS. Across all feather meal sources, there was a significant improvement in feed efficiency with increased levels of dietary CP (P ≤ 0.01). The PER results followed the same trend as feed efficiency (P ≤ 0.10), with respect to the EPFMCS and CFMCS diets having higher PER values than the PFMCS. Across all three sources of feather meal, there
Experiment 3 The metabolizable energy (TME and TMEn) contents of the three feather meals (PFM, EPFM, and CFM) were not significantly different (Table 6). The TAAA of the PFM and EPFM were consistently higher than what was observed for CFM (Table 7), and for lysine and threonine the differences were significant (P ≤ 0.05). The overall average amino acid availabilities of PFM and EPFM were 10.7 and 9.2% higher, respectively, than that of CFM.
DISCUSSION Similar to what was reported by Naber et al. (1961), the results of Experiment 1 showed that feather meal alone is not a particularly good protein source for poultry, even in diets that are high in CP. The lack of a growth response to the diets in Experiment 1 was most likely due to a combination of poor protein quality and the extremely fine texture of the semi-purified experimental diets, which were not conducive to sufficient intake to allow for positive N balance. The approach to Experiment 2, therefore, was to include a basal level of higher quality ingredients to assure a base line of growth and also to improve the consistency of the diet to facilitate feed intake. These two factors contributed to positive body
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BARBOUR ET AL. TABLE 5. Performance and response to protein quality of the poults fed the prepressed feather meal (PEMCS), enzyme-digested feather meal (EPFMCS), and commercial feather meal (CFMCS) diets from 7 to 19 d of age, Experiment 2 Feathermeal source PFMCS EPFMCS CFMCS
Dietary CP
BW gain
Feed intake
20 24 28 20 24 28 20 24 28
28.7 30.4 33.4 35.5 31.0 42.4 30.6 46.6 39.5 5.7
147 155 141 172 140 155 138 188 143 16.1
SEM Source of variation Feathermeal source Dietary CP Feathermeal by CP Main effect PFMCS EPFMCS CFMCS
0.23 0.35 0.42
0.76 0.54 0.19
30.8 36.3 38.9 31.6 31.6 38.4
20 24 28
148 156 157 152 152 146
Pectoralis major1
PER2
NPR3
0.20 4.05 0.20 3.79 0.23 3.71 0.20 3.97 0.22 3.43 0.27 3.55 0.22 4.14 0.25 3.88 0.28 3.84 0.02 0.16 Probabilities 0.09 0.09 0.01 0.02 0.89 0.89
0.96 0.81 0.81 1.00 0.91 0.97 1.07 1.01 0.98 0.09
1.88 1.54 1.52 1.87 1.72 1.60 2.06 1.62 1.66 0.26
0.10 0.29 0.94
0.16 0.0001 0.56
0.21 0.23 0.25 0.21 0.21 0.26
0.86 0.96 1.02 1.01 1.01 0.92
1.65 1.73 1.78 1.94 1.63 1.59
Gain/feed
3.85 3.65 3.95 4.05 3.70 3.70
1
Weight of the left pectoralis major divided by final body weight multiplied by 100. Protein efficiency ratio (Henry, 1965. PER = weight gain divided by protein intake. 3 Net protein ratio (Bender and Doell, 1957). NPR = (BW gain minus BW loss of birds fed the N-free diet) divided by protein intake. 2
weight gains in all treatments in the second experiment. Although the differences in PER (P ≤ 0.10) and net protein ratio (NPR) (P ≤ 0.16) due to source of feather meal were not significant, the clear direction in favor of the EPFMCS and CFMCS compared with the PFMCS support the hypothesis that enzyme processing did improve the quality of the experimental turkey feather meal. This latter conclusion was further supported by the in vitro pepsin digestibility data. Han and Parsons (1991) also reported a positive relationship between pepsin digestibility and chick growth in a comparison of seven feather meal sources. The TMEn values were in the range of those reported by Liu et al. (1989). The TAAA values for PFM and EPFM were similar to the data reported by Han and Parsons (1991) for conventional roosters and were considerably higher than the TAAA for CFM. The availability of cystine in the EPFM and CFM was considerably lower than what was reported by Han and Parsons (1991), but these two TABLE 6. Gross energy (GE), TME, and TMEn of the prepressed feather meal (PFM), enzyme-digested feather meal (EPFM), and commercial feather meal (CFM), Experiment 3 Feathermeal source PFM EPFM CFM Pooled SEM Probability of effects of feathermeal source
GE 5,449 5,325 5,673 – –
TME (kcal/kg) 3,750 3,427 3,511 212 0.56
TMEn 3,295 3,094 3,105 135 0.52
sources of feather meal also contained higher lanthionine concentrations than what has been reported previously. In the latter report (Han and Parsons, 1991), lanthionine was negatively correlated with the true availability of lysine and TSAA, which may be contributing to the lower availability of those amino acids in CFM. Other factors are also involved, however, because the enzyme-treated turkey feathers (EPFM) and CFM had similar lanthionine concentrations.
TABLE 7. True amino acid availability (TAAA) of prepressed feather meal (PFM), enzyme-digested feather meal (EPFM), and commercial feather meal (CFM), Experiment 3 Amino acids
PFM
EPFM
CFM
SEM
Methionine Cystine Lysine Arginine Tyrosine Threonine Serine Phenylalanine Aspartate Glutamate Proline Alanine Valine Isoleucine Leucine Histidine Mean
79.3 67.3 77.2a 86.7 83.5 82.2a 86.9 87.4 77.3a 81.9a 80.7a 84.4 86.8 88.1 85.7 78.3a 82.1
(%) 75.5 60.1 75.2a 85.6 83.9 81.0a 87.3 87.3 74.4a 80.9 79.6a 84.3 85.7 87.8 85.3 76.3a 80.6
69.7 54.3 60.4b 80.3 75.4 68.6b 77.4 82.9 47.7b 69.1b 67.7b 79.6 80.6 83.7 80.0 64.6b 71.4
2.92 4.64 3.21 2.50 2.60 3.16 2.87 2.44 4.54 3.06 3.43 2.43 2.55 2.33 2.62 3.40
a,b Means within rows with different superscripts are significantly different (P ≤ 0.05).
ENZYME PREDIGESTION AND FEATHER MEAL QUALITY
In summary, enzyme pre-digestion of turkey feathers prior to heat treatment improved the nutritional quality of the resulting feather meal when compared with untreated feathers in a poult growth assay. The treated feather meal (EPFM) was similar to a CFM in the poult growth assay but was superior to CFM with respect to amino acid availability when tested in precision fed roosters. The CFM contained higher levels of dietary fat than the EPFM, which might have positively affected CFM protein use in the growth study thus allowing for greater use of a lesserquality protein source. These results are opposite to what was observed for the rooster TAAA assay, however, and point out the ambiguity that can occur when different approaches are used to evaluate the quality of byproduct feed ingredients.
ACKNOWLEDGMENTS We wish to thank Dennis Hartzler, Cindy Coy, and John Nixon in the Department of Animal Sciences and the OARDC poultry research farm crew.
REFERENCES Baker, D. H., R. C. Blitenthal, K. P. Boebel, G. L. Czarnecki, L. L. Southern, and G. M. Willis. 1981. Protein-amino acid evaluation of stem-processed feather meal. Poult. Sci. 60:1865–1872. Bender, A. E., and B. H. Doell. 1957. Biological evaluation of proteins: a new aspect. Br. J. Nutr. 11:140–148. Han, Y., and C. M. Parsons. 1991. Protein and amino acid quality of feather meal. Poult. Sci. 70:812–822. Henry, K. M. 1965. A comparison of biological methods with rats for determining the nutritive value of proteins. Br. J. Nutr. 19:125–135.
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Likuski, H. J. A., and H. G. Dorrell. 1978. A bioassay for rapid determination of amino acid availability values. Poult. Sci. 57:1658–1660. Liu, J. K., P. E. Waibel, and S. L. Noll. 1989. Nutritional evaluation of blood meal and feather meal for turkeys. Poult. Sci. 68:1513–1518. McNab, J. M., and J. C. Blair. 1988. Modified assay for true and apparent metabolisable energy based on tube feeding. Br. Poult. Sci. 29:697–707. Moritz, J. S., and J. D. Latshaw. 2001. Indicators of nutritional value of hydrolyzed feather meal. Poult. Sci. 80:79–86. Naber, E. C., S. P. Touchburn, B. D. Barnett, and C. L. Morgan. 1961. Effect of processing methods and amino acid supplementation on dietary utilization of feather meal protein by chicks. Poult. Sci. 40:1234–1245. Nordheim, J. P., and C. N. Coon. 1984. A comparison of four methods for determining available lysine in animal protein meals. Poult. Sci. 63:1040–1051. National Research Council. 1994. Nutrient Requirements of Poultry. 9th rev. ed. National Academy Press, Washington, DC. Papadopoulos, A. R., A. R. Boushy, and E. H. Ketelaars. 1985. Effect of different processing conditions on amino acid digestibility of feather meal determined by chick assay. Poult. Sci. 64:1729–1741. SAS Institute. 1990. SAS User’s Guide: Statistics. SAS Institute Inc., Cary, NC. Scott, M. L., M. C. Nesheim, and R. J. Young. 1982. Nutrition of the Chicken. 3rd ed. M. L. Scott Associates, Ithaca, NY. Sibbald, I. R. 1986. The T.M.E. system of feed evaluation: methodology, feed composition data and bibliography. Tech. Bull. 1986-4E. Agriculture Canada, Ottawa, Canada. Sibbald, I. R., and P. M. Morse. 1983. The effects of feed input and excreta collection time on estimates of metabolic plus endogenous energy losses in the bioassay for true metabolizable energy. Poult. Sci. 62:68–76. Sibbald, I. R., and M. S. Wolynetz. 1985. Relationships between estimates of bioavailable energy made with adult cockerels and chicks: Effects of feed intake and nitrogen retention. Poult. Sci. 64:127–138.
