Recent data has indicated that interactions among the branched-chain amino acids, specifically valine and leucine, can negatively influence broiler performance and carcass traits. Therefore, an experiment was conducted to observe the interactive effects between dietary valine and leucine on live performance, carcass traits, and Pectoralis major myopathies of Cobb MV × 500 broilers. A corn/soybean meal basal diet was formulated to contain Val/Lys and Leu/Lys ratios of 72 and 130, respectively, with a digestible lysine level of 1.05%. Graded amounts of feed-grade L-valine and L-leucine were added in order to produce 12 experimental diets consisting of a 4 (Val/Lys: 72, 77, 82, 87) × 3 (Leu/Lys: 130, 150, 170) level factorial design. Diets were fed to eight replicate pens of 21 male broiler chicks. Body weight gain, feed intake, and feed conversion were determined for the 32 to 45 d finisher period. At d 46, four birds per pen were processed for determination of carcass traits and the incidence and severity of woody breast in P. major fillets. All data were analyzed by two-way ANOVA using SAS 9.4. Statistical significance was considered at P ≤ 0.05 and means were separated using a repeated t-test, when appropriate. No differences were observed for any live performance or carcass trait variable in response to dietary valine level, leucine level, or their subsequent interaction. Concerning woody breast, a significant interaction (P < 0.05) was observed for average score and the distribution of scores 1 and 2.
These data indicate that within the valine and leucine levels tested, branched-chain amino acid antagonism did not negatively influence broiler performance and carcass traits. The appearance of an interaction between valine and leucine for woody breast parameters was surprising and the mechanism behind the interaction is currently unknown.