Inheritance of changes in body weights over the laying cycle and their interrelationships with economic traits in White Leghorns

Two pure strains of White Leghorn, their reciprocal crosses and a control line were evaluated for changes in body weights between different intervals from 8 to 72 weeks of age. The three purebred stocks differed significantly in weight gain from 8 to 20 and from 20 to 40 weeks of age. However, the reciprocal crosses did not differ in body weight ratios at any of the consecutive ages. Crosses had significantly lower body weight ratios between 8 and 40 weeks of age in comparison to the pures. Heritabilities for early body weight ratios (8–40 weeks) were moderate (0.44±0.21) to low (0.11 ±0.15). Body weight ratios at later ages 40–56 and 56–72 had even lower heritabilities associated with large standard errors. The genetic correlations of ratio of consecutive body weights at early ages (i.e 8.20 and 40 week) with final body weight for that age were positive. Egg number to 40 weeks of age had low positive genetic correlation with early body weight ratios (i.e. 8.20 and 40 week).