Threonine requirement of broiler males from 42 to 56 days in a summer environment

Amino acid requirements of broilers may be altered during extreme environmental conditions. Threonine is a limiting amino acid for broilers, particularly at finishing when a hot environment would decrease feed intake. The dietary threonine requirement was examined with male broilers from 42 to 56 days of age during summer production. Birds were given a common feeding regimen until 6 wk of age, then six experimental diets consisting of progressive increments of threonine that ranged from 0.50 to 0.80% were fed from 42 to 56 days of age. Feed conversion was optimized at a total dietary threonine concentration approximating 0.67% of the diet; however, growth rate and feed consumption were not significantly affected by dietary threonine. Increasing dietary threonine did not alter carcass yield nor the proportions of abdominal fat and Grade A carcasses, but, breast fillet weight and its relative yield was maximized at 0.62% dietary threonine. Threonine need for male broilers is less for optimum breast meat recovery than feed conversion ratio during hot temperature conditions.