Determination of digestible valine requirements in male and female Cobb 500 broilers

Abstract Published literature elucidating dietary valine (Val) requirements for female broilers is limited and lacks data for the finisher phase. Three experiments (Exp) were conducted to determine the Val requirement for Cobb MX × 500 females during the grower (Exp 1; 14 to 28 days), finisher (Exp 2; 28 to 42 days), and withdraw periods (Exp 3; 42 to 56 days). Two additional Exp were conducted to determine the Val requirement for Cobb MV × 500 male (Exp 4) and female (Exp 5) broilers from 14 to 35 days. Corn-soybean meal diets were fed in the experimental period of all Exp to create Val dose response titration diets. Dietary titration levels of digestible Val to digestible Lys (Val/Lys) ratios were: 64 to 82 in Exp 1; 65 to 83 in Exp 2 and 3; and 57 to 92 in Exp 4 and 5. Body weight (BW) gain, feed intake, and feed conversion ratio were determined for each experimental period. At the conclusion of Exp 2 through 5, broilers were processed to determine carcass traits. Requirements were determined using regression analysis, considering the requirement to be 95% of the quadratic response. No significant linear or quadratic responses were determined for Exp 1 through 3. In Exp 4 and 5, significant responses were observed for feed conversion ratio, but not processing yields. The lack of responsiveness in Exp 1 through 3 are likely due to an inadequate reduction in dietary Val to observe female quadratic responses. Valine requirements were determined to be 78 and 77 Val/Lys for males and females, respectively, based on feed conversion responses.