Effect of reducing body weight variability on the sexual maturation and reproductive performance of broiler breeder females

A study was performed to assess the effect of reducing BW variability on sexual maturation and reproductive performance of broiler breeder hens. A total of 208 Ross 708 1-d-old pullets were randomly assigned at hatch to 1 of 2 feed allocation treatments starting at 16 wk of age when all birds were placed in individual cages. A control treatment had feed allocated on a group basis (GRP) and followed the recommended BW target. A second treatment had feed allocated on an individual bird basis (IND). By design, the BW of IND pullets converged at 20 wk. This design dictated that IND birds had a lower BW variability and a higher feed intake variability than GRP birds. Pullets were retrospectively classified into 3 initial (16 wk) BW categories: low, average, or high, using the mean +/- 0.5 SD as threshold. After their first egg, 64 birds were killed and dissected for determination of fleshing, fatness, and reproductive morphology. Egg production traits were analyzed to 60 wk, when the remaining birds were killed and dissected. Reducing BW variability did not reduce variability of age, follicle numbers, and ovary and oviduct weight at sexual maturity. The IND feed allocation accelerated the onset of production of low BW birds, which increased total egg production (177 eggs) and average sequence length (3.9 d) with respect to GRP x low birds (163 eggs; 3.0 d). However, IND x low hens produced more eggs < 52 g than GRP x low hens (22 versus 8 eggs). The IND treatment increased variability of ovary weight, large yellow follicle number, and large yellow follicle weight at 60 wk. Reducing BW variability increased variation in ovarian morphology at the end of production, which suggests that optimal BW for reproduction varied among birds. Correcting BW from 16 wk to reach the BW target primarily affected low initial BW pullets, which entered lay sooner and produced more eggs, although 91% of the additional eggs weighed < 52 g.