Laying Performances and Genetic Parameters in Some Breeds of Chickens

Abstract

The genetic and phenotypic correlations between egg weight and some economic traits using three years' data of White Leghorns consisting of two strains (WL-D, WL-E), Barred Plymouth Rocks (BPR), New Hampshires (NH) and Rhode Island Reds (RIR), which were just the same those used in the preceding report, (Saeki et al., Japan. Poultry Sci., 3, 76, 1966), were estimated. A total of 885 pullets produced from 381 dams and 120 sires were available for study. Egg weight and egg number were recorded individually every day throughout the pullet year.There existed a positive correlatation of 0.2-0.6 between average weight of the first egg and average egg weight in pullet year. The genetic and phenotypic correlations between egg weight and body weight at the first egg, and between egg weight and age at the first egg were estimated to be +0.3-+0.5 except for NH and RIR and +0.3-+0.6, respectively.The correlation between egg weight and survivors' egg production was the range of -0.2--0.4, suggesting simultaneous selection for these two traits seems to be difficult in the same strain.A negative correlation between egg weight and time interval from the first egg to average egg weight was estimated in most cases. It suggests that the heavier the weight of the first egg is, the shorter is the time interval to reach the mature weight.