Digestible Valine Requirements of Growing-Finishing Ross 308 Broilers

SUMMARY Three experiments were conducted to assess the digestible valine (dVal) requirements of growing-finishing Ross 308 broilers. In the first experiment, the limitation of valine in low crude protein diets was evaluated. Based on this first experiment, it can be concluded that Val is a limiting amino acid (AA) in broiler diets and when broilers are fed a CP-reduced diet with a dVal:Lys ratio lower than 80%, growth performance but not carcass composition is significantly affected. The second experiment was conducted to evaluate the growth performance response to dietary digestible lysine (dLys) and to validate the adequate AA profile to be used in a dose–response experiment. A dLys content of 10.5 g/kg in grower and 8.5 g/kg in finisher diets under the applied AA profile can be considered as suboptimal for Ross 308 broilers. In the third experiment, the optimal dVal:Lys ratio for Ross 308 broilers in a dose-dependent manner was evaluated. The quadratic broken line model estimated the optimal ratio for dVal/Lys at 83.3 for average daily gain and at 84.6 for average daily feed intake over the whole fattening period. Valine is therefore a limiting AA for performance and must be controlled when dietary crude protein is reduced.