The objective of this study was to estimate the variance components for body weight in Japanese quails by Bayesian procedures. The body weight at hatch (BWH) and at 7 (BW07), 14 (BW14), 21 (BW21) and 28 days of age (BW28) of 3,520 quails was recorded from August 2001 to June 2002. A multiple-trait animal model with additive genetic, maternal environment and residual effects was implemented by Gibbs sampling methodology. A single Gibbs sampling with 80,000 rounds was generated by the program MTGSAM (Multiple Trait Gibbs Sampling in Animal Model). Normal and inverted Wishart distributions were used as prior distributions for the random effects and the variance components, respectively. Variance components were estimated based on the 500 samples that were left after elimination of 30,000 rounds in the burn-in period and 100 rounds of each thinning interval. The posterior means of additive genetic variance components were 0.15; 4.18; 14.62; 27.18 and 32.68; the posterior means of maternal environment variance components were 0.23; 1.29; 2.76; 4.12 and 5.16; and the posterior means of residual variance components were 0.084; 6.43; 22.66; 31.21 and 30.85, at hatch, 7, 14, 21 and 28 days old, respectively. The posterior means of heritability were 0.33; 0.35; 0.36; 0.43 and 0.47 at hatch, 7, 14, 21 and 28 days old, respectively. These results indicate that heritability increased with age. On the other hand, after hatch there was a marked reduction in the maternal environment variance proportion of the phenotypic variance, whose estimates were 0.50; 0.11; 0.07; 0.07 and 0.08 for BWH, BW07, BW14, BW21 and BW28, respectively. The genetic correlation between weights at different ages was high, except for those estimates between BWH and weight at other ages. Changes in body weight of quails can be efficiently achieved by selection

RESUMO -Foram coletados dados de peso do ovo, altura de albúmen, espessura da casca, peso corporal e produção total de ovos aos 90 dias de postura de três linhagens de codornas de postura (Coturnix coturnix japonica) alimentadas com rações contendo 2.900 ou 2.500 kcal de energia metabolizável para verificar a existência da interação genótipo × ambiente.Utilizou-se o programa computacional MTGSAM, que permite inferência bayesiana, usando amostragem de Gibbs, aplicado a um modelo animal, para estimar os componentes de covariâncias, herdabilidade e correlações genéticas entre os dois ambientes. Por meio dos resultados de herdabilidade e correlações genéticas, concluiu-se que houve interação genótipo × ambiente somente para as características altura de albúmen e espessura da casca. As características peso do ovo e peso corporal são passíveis de ganhos genéticos, independentemente do nível de energia da ração, enquanto a produção de ovos tem baixo potencial para ganhos genéticos se a seleção for baseada em recordes parciais.Palavras-chave: altura de albúmen, espessura da casca, herdabilidade, peso corporal, peso do ovo, produção de ovos Genotype-environment interaction in laying quail fed diet with two levels of metabolizable energyABSTRACT -Data of egg weight, albumen height, shell thickness, body weight and egg production at 90 days of laying from three lines of laying quails (Coturnix coturnix japonica), fed diets with 2,900 kcal or 2,500 kcal metabolizable energy, were used to check the existence of the genotype-environmental interaction. The MTGSAM software program was used, which allows Bayesian inference, using the Gibbs Sampling, applied to an animal model, to estimate the co-variance components, heritability and genetic correlation between both environments. The results of heritability and genetic correlations showed that there was a genotype-environment interaction only for albumen height and shell thickness. The traits egg weight and body weight are susceptible to genetic gains regardless of the diet energy level, while egg production has low potential for genetic gains if the selection is based on partial records.Key Words: albumen height, body weight, egg production, egg weight, heritability, shell thickness IntroduçãoA criação de codornas de postura tem como principal objetivo a produção de ovos, um produto muito apreciado pelos consumidores e com boas qualidades nutricionais. De acordo com o National Research Council (1994), as rações para codornas devem conter 24% de proteína bruta (PB) para aves em crescimento, 20% de PB para aves em postura e 2.900 kcal de energia metabolizável (EM). Essas informações, no entanto, são antigas e nem sempre estão de acordo com o potencial genético do animal e com seu ambiente de criação.A estimação das características qualitativas do ovo é importante para os processos de seleção e melhoramento genético, que podem ser conduzidos de forma a atender às necessidades do criador ou do consumidor.Os métodos indicados para estimação dos componentes de covariância já estão rel...