Evaluation of branched-chain amino acids in male Cobb MV x 500 broiler chickens by using Box-Behnken response surface design

摘要

Data pertaining to the branched-chain amino acids (BCAA) are of particular importance due to the positioning of valine (Val) and isoleucine (Ile) as limiting amino acids (AA) in conventional diets. Similarly, current research evaluating their potential interaction is sparse. Therefore, two experiments were conducted using Box-Behnken design (BBD) to determine performance and carcass responses to BCAA and glycine (Gly) supplementation in male broilers from 15-34 days (Experiment 1) and 15-35 days (Experiment 2). In Experiment 1, 13 experimental diets were formulated to contain various levels of digestible BCAA supplementation based on BBD. Inclusion levels for the BCAA were based on ratios to digestible lysine (Lys) and included: 65, 75, and 85 for digestible Val; 58, 66, and 74 for digestible Ile; and 110, 130, and 150 for digestible leucine (Leu). Diets for Experiment 2 were formulated in a similar manner and design, but total glycine + serine (Gly + Ser) inclusions were substituted for Leu. Inclusion levels were the same for Val and Ile as in Experiment 1 and ratios to digestible Lys of 131, 151, and 171 for total Gly + Ser. Fifteen-hundred and sixty male broilers were distributed across 78 pens and randomly assigned to 13 experimental diets in each Experiment. Body weight (BW) gain, feed intake, and feed conversion ratio (FCR) were determined for the experimental grower period in both Experiments. On day 35 (Experiment 1) or 36 (Experiment 2), six birds per pen were processed for the evaluation of carcass traits. Data were analyzed for linear, quadratic, and interactive effects. In Experiment 1, increased Leu inclusion linearly increased (P < 0.10) FCR at 35 days and interactions between Ile and Val were observed for BW gain (P < 0.10) and FCR (P < 0.05). Interactions between Ile and Val and Leu and Val significantly affected breast meat weight (P < 0.10) and yield (P < 0.05). These interactions were primarily driven by the inclusion of Val, which depressed breast meat yield, although no linear or quadratic effects of Val were detected. In Experiment 2, interactions between Gly + Ser and Ile were found on total breast yield (P < 0.10). Interactions were also observed between Ile and Val, and Gly + Ser and Val for leg quarter yield (P < 0.10). Unlike in Experiment 1, interactions between Ile and Val were not observed for BW gain, FCR, or total breast yield. Results from these experiments highlight the importance of evaluating relevant in-teractions between potentially co-limiting AA when conducting trials determining AA requirements.