Genetic parameters from univariate and bivariate analyses of egg and weight traits in Japanese quail

Fully pedigreed records of a Japanese quail population were analyzed for genetic parameters of egg and BW traits. A restricted maximum likelihood (REML) procedure was applied in univariate and bivariate analyses. Quantitative genetic analyses, including maternal effects, were carried out on the records of 947 male and 861 female birds (total = 1,808). The traits were analyzed with bird as a random factor to fit the additive direct effect, bird being the individual for which the trait was recorded, namely hen (dam) for egg traits and chick (progeny) for BW. Permanent environmental effects (0.29 to 0.35) on egg traits were higher than corresponding heritabilities (0.18 to 0.25). Significant maternal genetic and maternal permanent effects were measured for hatching BW. The heritabilities of weekly BW were low, and decreasing by 5 to 6 wk of age. They were 0.07, 0,18, 0.19, 0.18, 0.19, 0.13, and 0.15 from hatching to 6 wk, respectively. Strong correlations were detected between direct genetic effects for egg traits and maternal genetic effect for BW traits. Applying such detailed analyses in the study of both egg and BW traits provides procedures to specifically evaluate Japanese quail and poultry in general. The results illustrated that the maternal permanent environmental effects made larger contributions to the variability of egg traits than did direct genetic effects. This situation implies that rearing of birds, healthcare, and feeding are very important determinants of egg characteristics.