Differential response of body weight at, and growth curves to 20-weeks on production traits in female broiler breeders

One thousand seven hundred sixty three broiler breeder females of the strain PB-2 developed at Punjab Agricultural University, Ludhiana were selected on the basis of 5-week body weight from a population of five thousand two hundred and eighty two birds. Feed restriction was imposed and the birds were allowed to grow on three different growth curves to the age 20-weeks as to attain a proportional target body weight (BW) of 0.8, 1.0 and 1.2 of the standard BW recommended for the strain. The birds grown on standard growth curve were allowed to attain a BW of 2150g through five different curves, one linear and two each concave and convex. The pullets having higher BW at 12-weeks of age exhibited better egg size, while those grown on a concave curve and provided ample feed stimuli to attain a rapid growth during the reproductive organ development phase (12 to 20-weeks period) produced relatively more eggs. The shape of growth curve had a significant effect on age at sexual maturity (ASM), egg production to 40 and 52-weeks of age and egg weight. ASM had a negative correlation (−0.32 to -0.92) while egg production and egg weight had a medium to high positive correlation (0.13 to 0.98) with body weights at different ages.