Energy metabolism of broiler breeder hens. 1. The partition of dietary energy intake.

The partitioning of AME intake (MEI) and recovered energy (RE; defined as MEI minus heat production) was investigated on Hubbard broiler-breeder hens (BB) by using indirect calorimetry and energy balance. The regression of RE on MEI was linear (R2 = .96; P less than .01) with a slope of .817 +/- .024 (SE) and a y-intercept of -238.3 +/- 10.7 (SE). The maintenance energy requirement was 292 kilojoule (kJ) per kg per day (367 kJ per kg.75 per day). The regression of body RE, defined as RE minus egg energy, on MEI was linear (R2 = .96; P less than .01) with a slope of .799 +/- .045 (SE) and a y-intercept of -344.9 +/- 19.7 (SE). Therefore, an MEI of 432 kJ per kg per day was required by BB hens to maintain body energy equilibrium when they were laying at approximately 85% production. At an MEI of less than 432 kJ per kg per day, body energy was used for egg production. The AME cost of depositing 1 kJ of body, egg, protein, or fat energy was (mean +/- SE) 1.21 +/- .06, 91 +/- .32, 1.96 +/- .71, and 1.05 +/- .15 kJ, respectively. The results indicate that individually caged BB hens between 28 and 36 wk of age in a thermal-neutral environment (21 C) require approximately 1.6 megajoule (MJ) of AME per bird per day for normal growth (3 g/per day) and egg production (85%).