Comparisons of male and female broiler responses to dietary threonine from42 to 56 days of age

Females approximate 30% of the broilers marketed for further processing. Th e need for threonine for females is known to be less than for males during the first few weeks of production; however, information is limited on any d ifference thereafter, This study examined responses of male and female feat her-sexable broilers to diets formulated to contain three concentrations of threonine (0.52, 0.63, and 0.74% total) from 42 to 56 d of age. Male broil ers optimized growth rate and feed to gain ratio when threonine approximate d 0.74 % of the diet; 0.63 % dietary threonine was more appropriate for fem ales. Dietary threonine concentration did not influence chilled carcass yie ld, abdominal fat percentage, or the proportion of "A" Grades. In agreement with live performance, males optimized fillet weight with 0.74% dietary th reonine; 0.63% was adequate for females. The need for dietary threonine to optimize live performance and recovery of the breast fillets is less for fe males than for males during 42 to 56 d of age.