This trial was conducted to evaluate the dietary levels of digestible threonine for growing gilts on heat stress environment. Seventy crossbreed gilts averaging initial weight of 14.9 ± 0.56 kg were assigned to a complete randomized blocks design with five treatments (levels of digestible threonine) of seven replications (two animals per experimental unity). The treatments consisted of the following dietary digestible threonine levels: 0.538, 0.577, 0.614, 0.651, and 0.688%. Daily weight gain and threonine intake linearly increased as the dietary threonine level increased, whereas daily feed intake was not affected. Although feed:gain ratio linearly changed with the treatments, the best dietary digestible threonine level was estimated in 0.587%. Daily depositions of protein and fat in the carcass and absolute and relative weights of the evaluated organs were not affected by the treatments. It was concluded that gilts from 15 to 30 kg on heat stress environment require 0.587% of digestible threonine in the diet to obtain better feed:gain ratio, leading to a threonine digestible: digestible lysine ratio of 63%.
performance; temperature; threonine:digestible lysine ratio
