Restricted food intake and reproductive performance of broiler breeder pullets

Synopsis

The effect of restricted feeding during the rearing and laying periods on the reproductive performance of a total of 1920 pullets from two commercial broiler dam lines was examined. The rearing treatments which commenced at 10 weeks of age were: A—ad libitum, B—80%, C—60% and D—40% of ad libitum. The restricted birds were fed on alternate days. The laying treatments, which commenced at 21 weeks of age, were X—ad libitum, Y—90% and Z—80% of ad libitum and the restricted birds were fed every day. The experimental design was a fully symmetrical factorial with all rearing: laying treatment combinations represented.

Sexual maturity was progressively delayed by increasing severity of restriction during rearing and by increasing severity of restriction during laying in birds reared on treatments G and D. Mortality during rearing was lowest amongst birds reared on treatments B and C. At 25 weeks of age several birds died as a result of a heat wave and mortality was directly related to food intake at the time and to food intake during the rearing period.

In birds which had been restricted during rearing which were allowed to feed ad libitum during laying, compensatory food consumption occurred. This compensation was proportional to the degree of restriction and there was an associated increase in body weight. Mortality during laying, excluding that due to heat stress, was highest in the birds fed ad libitum and lowest in those most severely restricted; there was no effect of rearing treatment on this parameter. Production of hatchable eggs (> 50 g) per hen d to 67 weeks of age was highest in birds restricted during rearing and fed ad libitum during the laying period. In birds of the heavier strain (1) the combination of treatments D and X produced the greatest number of hatchable eggs while in the lighter strain (2) B and X, and D and X caused the highest production. Restricted feeding during rearing caused increased egg weight at 32 and 40 weeks of age in strain 2 but not in strain 1. In both strains the highest net returns were associated with the combination of treatments D and X; compared with the AX treatment $1.82¹ more per bird was returned by strain 1 and $1.56 by strain 2.

The results suggest that relatively severe food restriction during rearing followed by ad libitum feeding during laying may be the best feeding regime for broiler breeders.