The objective was to estimate direct and maternal genetic effects for body weight at different ages of Japanese quail. Genetic and phenotypic correlations were also estimated among body weight traits. In the first generation, 96 male and 192 female birds were randomly selected and one male with two females were assigned in each cage. Body weight traits were recorded from offspring at hatching day and 7, 14, 21, 28, 35 and 42 days of age. Restricted maximum likelihood (REML) procedure was applied to analyses body weight traits. Heritabilities were estimated using 3 animal models consisting additive direct genetic effect (model1), additive direct and maternal genetic effects (model2) and additive direct, maternal genetic and maternal permanent environmental effects (model3). Likelihood ratio test was used to find out the best model for each trait. Model2 was evaluated to be the best for body weight traits except weight at hatching day (BW0). For BW0, model 3 was the best. Estimated direct heritability for BW0 was 0.15 and for 7, 14, 21, 28, 35 and 42 days of age were 0.15, 0.19, 0.25, 0.24, 0.32 and 0.42, respectively. Estimated maternal heritability for BW0 was 0.60 and for 7, 14, 21, 28, 35 and 42 days of age were 0.29, 0.24, 0.27, 0.30, 0.16 and 0.14, respectively. There was an increasing trend for direct genetic effect and a declining trend for maternal genetic effect from BW0 to BW42, suggesting that maternal genetic effect is less important at older ages. The highest and the lowest genetic correlations between direct and maternal genetic effects were detected at 35 (–0.49) and 28 days of age (–0.87), respectively. The highest genetic and phenotypic correlations were found between BW28 and BW35 (0.99 and 0.83, respectively). Present results suggest that body weight at hatching day couldn't be used as a selection criterion to improve body weight at slaughter age (BW35 or 42) and it is better to select birds based on BW7, instead.

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