Effects of environmental temperature,dietary energy,sex and age on nitrogen and energy retention in the edible carcase of broilers

1. Two environmentally‐controlled houses, one set at constant 21°C (low temperature, LT) and the other set at diurnally cycling 21°C to 30°C (high temperature, HT), and two dietary energy concentrations of 13 MJ ME/kg (low energy, LE) and 13.8 MJ ME/kg (high energy, HE) were used to study nitrogen and energy retention in the edible carcase of male and female broilers slaughtered at 34 and 54 days.

2. Carcase nitrogen was higher in males than in females, and in birds reared at LT than in those reared at HT.

3. Birds at LT and on HE diet, regardless of sex, retained more energy as fat in their carcases than those at HT and on LE diet respectively.

4. Maintenance energy requirement averaged 6.70, 7.67, 7.43 and 9.01 kJ per g metabolic body size (kJ/gW 0.66) for broilers at HT and LT up to 34 d and at HT and LT up to 54 d, respectively.

5. There was a similar increase with age in the energy requirement for growth but with requirements of broilers at LT consistently lower than for those at HT.