Evaluation of National Research Council amino acid recommendations for large white turkeys

Effects of decreases in the three most limiting amino acids of low protein diets at two different feeding periods in Japanese quails

1. Diets containing 100 (AA100), 95 (AA95), 90 (AA90) or 85% (AA85) of National Research Council (NRC, 1994) recommendations of methionine, threonine and lysine in a low-protein diet (200 g/kg) were fed to 15-d-old quails. 2. Decreases of up to 15% of NRC recommendations in these three amino acids did not affect feed intake, weight gain and gain:feed intake values in the 15-35- and 15-42-d feeding periods. 3. Compared to control diet, feeding cost per bird was lower in males fed with AA95 and AA85 at 15-35 d and with AA85 diets at 15-42 d. At 15-35 d, feeding cost per 100 g weight gain was lower in both males and females receiving the AA85 diet while at 15-42 d it was lower in males fed with AA85 and females fed with AA90 compared to the control diet. Feeding cost calculated based on 100 g weight gain resulted in more meaningful results than cost calculated for the production of a bird. 4. Dietary amino acid content did not significantly affect carcase, thigh (bone in and skin on) or breast meat (deboned and skin on) yields. Males fed with AA90 diet and females fed with AA90 and AA85 had lower protein contents in their breast meat (without bone and skin) compared to the ones fed with control diet.

Decreasing broiler crude protein requirement by methionine supplementation

The experiment was conducted with two levels of protein (23 and 20% in starter, 20 and 18% in grower) and three levels of methionine (NRC, 110 of NRC and 120% of NRC in starter and grower stages). No significant differences were found for protein, methionine or their interaction on Feed Intake (FI) and Feed Conversion Ration (FCR) for starter and grower, with the exception of an interaction of 20% CP and 0.46% (120% ofNRC) methionine which significantly improved (p < 0.05) the FCR compared with 18% CP and 0.38% (NRC) level ofmethionone, at the grower stage. Carcass yield and breast meat were significantly (p < 0.05) increased by 23% Crude Protein (CP) compared to 20% in starter. In contrast, abdominal fat was significantly decreased (p < 0.05) by 23 and 20% CP diet in starter and grower, respectively compared to the other levels of CP as well as by high levels of methionine. In the interaction of 20% CP and high level of methionine (0.46%) on carcass yield, a significant increase (p < 0.05) was found in grower stage compared with 18% CP and both 0.38% and 0.42% (110% of NRC) of methionine levels. A similar effect was found on breast meat yield compared with interaction of both 0.5% (NRC) and 0.55% (110% of NRC) of methionine and 20% CP at 21 days, as well as at 42 days of age with 0.38% methionine and 18% CP. Finally, the results of this study, have suggested that methionine/CP ratio could be adjusted at 0.024% (0.024 g methionine/per g crude protein) in starter and 0.023% for grower. Decreased CP in the diet, increased breast meat yield and reduction of abdominal fat were achieved by these ratios of methionine/protein.

Growth responses to dietary lysine at high and low ambient temperature in male turkeys

Several researchers have postulated that dietary lysine requirements for turkeys are dependent upon ambient temperature. To test and quantify this hypothesis, a factorial experiment was designed with four dietary lysine levels (75, 90, 105, and 120% of NRC lysine recommendations) from 1 d of age onward and two ambient temperatures (15 vs. 30 degrees C) from 4 wk of age onward. Growth performance and carcass yields were measured, and requirements were derived from the fitted exponential response curves at 95% of the maximum possible response above that of the basal diet. In the entire experiment no significant interaction effects between temperature and lysine were observed for feed intake, BW gain, and feed:gain ratio. Exponential curves gave a very good fit (R2 > 0.89) for feed intake, and BW gain responses to dietary lysine concentrations in all age intervals. The dietary lysine requirement was estimated to be 1.67 +/- 0.09%, 1.19 +/- 0.13%, 1.08%, and 0.94 +/- 0.35% from 29 to 56 d, 57 to 84 d, 85 to 114 d, and 115 to 140 d of age, respectively. High temperature decreased all absolute processing yields in kilograms but relative cold carcass yield and relative yields of thighs, drums, and wings were increased by high temperature. Relative breast meat yield and abdominal fat were decreased by high temperature. Turkeys at low temperature responded with more breast meat to high lysine than at high temperature.

Dietary arginine and lysine in Large White toms. 1. Increasing arginine:lysine ratios does not improve performance when lysine levels are adequate

A study was conducted utilizing two strains of male Large White turkeys (BUT Big 6 and Nicholas 700) to determine the effects of increasing Arg:Lys ratios on live performance and carcass composition. Diets were formulated to provide 100, 110, and 120% of NRC (1994) Lys levels, adjusted for dietary energy level, with Arg:Lys ratios of 1.0:1, 1.1:1, 1.2:1, and 1.3:1 in a 3 x 4 factorial arrangement. Eight pens of 15 poults (four pens of each strain) were fed each of the 12 test diets for an 18-wk period. Diets were changed at 3-wk intervals rather than the 4-wk interval suggested by NRC. The results of this study suggest that the Arg and Lys levels suggested by the NRC (1994) are not sufficient when diets are fed on 3-wk intervals, rather than the 4-wk intervals suggested by NRC. This conclusion is in agreement with the studies of Waldroup et al. (1997b). Increasing Arg:Lys ratios improved performance of turkeys only when the diets contained insufficient amounts of Arg in association with low levels of Lys. Increasing Arg:Lys ratios when diets contained sufficient amounts of these two amino acids was without benefit, in contrast to the report of Brake et al. (1994). Turkeys of the BUT Big 6 strain appeared to be more sensitive to marginal deficiencies of Lys and Arg than did turkeys of Nicholas 700 strain.

Response of two strains of large white male turkeys to amino acid levels when diets are changed at three- or four-week intervals

A study was conducted to evaluate the amino acid recommendations of the NRC (1994) when diets were changed at 3- or 4-wk intervals. Diets formulated to provide from 90 to 115% of recommended amino acid levels were fed to Nicholas (NIC) and British United Turkey (BUT) Large White males from day-old to 24 wk of age; samples of turkeys were processed at 18 and 24 wk. Results indicated that the amino acid levels suggested by NRC are adequate to support maximum body weight gain, feed conversion, and dressing percentage of Large White males grown to 18 or 24 wk when fed on 4-wk intervals. An approximately 5% higher level of amino acids was required to maximize breast yield. When feeds were changed at 3-wk intervals, higher levels of amino acids were required to maximize performance; however, there did not seem to be any difference in the response of the two strains of turkeys to different levels of amino acids in this study.