Optimum ratio of standardized ileal digestible tryptophan to lysine for piglets

Abstract

Two experiments were conducted to determine optimal standardized ileal digestible SID tryptophandysine ratio for piglets using growth performance and plasma urea N as response criteria. In Experiment 1, piglets were fed 6 diets with 8.5, 9.5,10.5,11.5, 12.5 or 13.5 g • kg-1 SID lysine to estimate lysine requirement. In Experiment 2, piglets were fed 6 diets with 9.2 g • kg-1 SID lysine, and 0.178, 0.182, 0.196, 0.216, 0.227 or 0.236 SID trytophandysine to estimate optimal tryptophandysine ratio. The SID lysine requirement was estimated to be 10.2 g • kg-1. Response criteria measured were unaffected by SID tryptophandysine ratio, implying that the diets fed were not deficient in tryptophan. In conclusion, the SID lysine requirement for the piglets was close to the recommendation by NRC (1998; 10.1 g • kg-1), but not NRC (2012; 12.3 g • kg-1). The optimal SID tryptophandysine ratio of the piglets was either equal to or less than 0.178.