Effects of energy and protein allowances during lay on the reproductive performance of broiler breeder hens

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Abstract
1. Broiler parent stock were fed daily allowances of 1.88, 1.73 or 1.52 MJ apparent metabolisable energy (AME) per bird at two different daily protein intakes (27, 21.3 g crude protein (CP) per bird) or daily protein intakes of 24.6 and 19.4 g CP per bird at a daily energy intake of 1.88 MJ AME per bird from 21 to 64 weeks of age. 2. Body‐weight gain and carcass fat and water content increased and fertility decreased with increasing energy allowance. Maximum egg production occurred at an energy intake of 1.73 MJ AME/bird d. 3. Differences in egg weight and hatchability were related to differences in both energy and protein intake. The highest egg weight occurred at the highest allowance of energy and protein. Hatchability was depressed where the daily allowances of protein and energy were in a ratio of more than 15 g protein: 1 MJ AME. 4. Apart from egg size no significant effects on reproductive performance were observed when dietary protein intake was varied from 27 to 19.5 g/bird d. 5. Requirements of broiler breeder hens for protein during lay may be lower than previously thought. For the strain used a protein intake of 19.5 g/bird d appeared adequate provided essential amino acid concentrations were maintained. 6. The close relationships between body weight and energy allowance and the latter and egg production make body‐weight gain a useful guide to management. A body‐weight gain of about 1.1 kg from 21 to 36 weeks of age was associated with optimum performance in this study.