This study was carried out to evaluate the requirement of digestible threonine in diets of gilts from 30 to 60 kg, maintained thermoneutral environment. Seventy crossbreed gilts with an initial weight of de 30.0 ± 0.61 kg were used in a randomized blocks design, with five treatments (levels of digestible threonine), seven replicates and two animals per experimental unity. The treatments corresponded of the levels of 0.50; 0.53; 0.56; 0.60; and 0.63% of digestible threonine. No effect was observed of digestible threonine level on daily weight gain of animals. Feed:gain ratio improved in a quadratic way with the digestible threonine level, and the Linear Response Plateau model estimated in 0.52% the level of amino acid, from which the feed conversion did not change. Daily feed intake was reduced with the increase of digestible threonine intake. Fat deposition linearly reduced, while protein deposition did not change with the increase of digestible threonine. The absolute and relative weight of kidneys and the absolute of intestine increased in a quadratic way with the digestible threonine levels, However, the relative weight of intestine increased in a linear way. It was concluded that the calculated level of 0.52% of digestible threonine, corresponding to a daily intake of 9.18 g and a relation with the digestible lysine of 63% provided better feed:gain ratio for gilts maintained in a thermoneutral environment from 30 to 60 kg.
environmental temperature; digestible threonine; gilts; performance
