Male and Female Broiler Responses to Low and Adequate Dietary Threonine on Nitrogen and Energy Balance

This study evaluated nitrogen and energy utilization by male and female broilers that were at 46 and 54 d of age fed diets deficient or adequate in threonine. Birds were reared in floor pens of an open-sided house and were provided diets that met NRC (1994) nutrient recommendations from placement until 6 wk of age. At 42 d, 48 birds (24 per sex) were selected and individually penned in Petersime batteries and were given feeds that were formulated to contain 0.52 or 0.74% total threonine having 18% CP and 3,200 kcal ME/kg. Two 24-h excreta collection periods were conducted on Days 46 and 54 to assess nitrogen and energy recovery. Males receiving adequate threonine had an advantage in retention of nitrogen and recovery of AMEn over males consuming the low threonine diet. Utilization of nitrogen by females was similar at both threonine concentrations, and AMEn corresponded to the concentration recovered by males when threonine was adequate. Inadequate threonine appears to create conditions that reduce recovery of energy by male broilers.