Comparisons of Male and Female Broiler Responses to Dietary Threonine from 42 to 56 Days of Age

SUMMARY Females approximate 30% of the broilers marketed for further processing. The 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 difference thereafter. This study examined responses of male and female feather-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 broilers optimized growth rate and feed to gain ratio when threonine approximated 0.74% of the diet; 0.63% dietary threonine was more appropriate for females. Dietary threonine concentration did not influence chilled carcass yield, abdominal fat percentage, or the proportion of “A” Grades. In agreement with live performance, males optimized fillet weight with 0.74% dietary threonine; 0.63% was adequate for females. The need for dietary threonine to optimize live performance and recovery of the breast fillets is less for females than for males during 42 to 56 d of age.