Digestible valine requirements in high protein diets for broilers from twenty-one to forty-two days of age

The present study was conducted to estimate dietary valine (val) levels to optimize growth performance and processing yields of an early growth broiler strain fed a high protein diet. A total of 1575 Cobb × Cobb 500 male broilers were fed a common starter diet to 21 d of age. From 21 to 42 days broilers were given all vegetable maize–soybean meal experimental diets. A basal diet formulated with 6.4 g digestible (dig) Val/kg and a summit diet with 9.7 g dig Val/kg, both having all other essential amino acids (AA) above recommendations, were mixed to produce seven diets with progressive increments of 6 g dig Val/kg. Each treatment had 9 replicate pens of 25 birds. Requirements of dig val were estimated using quadratic regressions and the broken line model. Estimations of requirements were of 8.5 and 8.2 g dig Val/kg for body weight gain, 8.4 and 8.1 g dig Val/kg for feed conversion ratio and 8.5 and 7.3 g dig Val/kg for abdominal fat yield using quadratic and broken-line models, respectively. No differences among treatments were detected for carcass and commercial cuts. The requirements determined in this study were higher than usually recommended for broiler males from 3 to 6 weeks. However, the calculated ratios of dig val to dig lysine of 77% and 76% for body weight gain and feed conversion ratio are similar to recently published data.