Comparative meta-analysis of broiler and piglet response to dietary valine taking into account isoleucine and leucine interactions

The aim of this study was to quantify the response of broilers and piglets to dietary valine (Val) level and the impact of the 2 other branched-chain amino acids (BCAA), leucine (Leu) and isoleucine (Ile), on this response through a meta-analysis approach. The databases were composed of 23 articles published between 1999 and 2018 and included 44 experiments and 229 treatments for broilers and 16 articles published between 2001 and 2018 and including 23 experiments and 126 treatments for piglets. Multiple regression models were fitted with the MIXED procedure of Minitab software with the random effect of the experiment. The Y variables were average daily gain (ADG), average daily feed intake (ADFI) and feed conversion ratio (FCR). The main X variable was dietary standardized ileal digestible Val (SID Val) and the other ones were dietary standardized ileal digestible Leu (SID Leu) and dietary standardized ileal digestible Ile (SID Ile). The response for ADG and ADFI to SID Val was positive linear and quadratic for broilers and piglets (broilers, ADG: P