Bayesian hierarchical model for comparison of different nonlinear function and genetic parameter estimates of meat quails.

This study aimed to compare different nonlinear functions to describe the growth curve of European quails and to estimate growth curve parameters, (co)variance components, and genetic and systematic effects that affected the curve using a hierarchical Bayesian model that allows joint estimation. Three different models were fitted in the first stage (Gompertz, Logístic, and von Bertalanffy). The analyzed data set had 45,965 records of 6,838 meat quails selected for higher body weight at 42 d of age for 15 successive generations, weighed at birth, 7, 14, 21, 28, 35, and 42 d of age. Comparisons of the overall goodness of fit were based on deviance information criterion (DIC) and mean square error. Gelfand's check function compared the models at different points of the growth curve. In the second stage, the systematic (sex and generation) and genetic effects were considered in an animal model. Random samples of the a posteriori distributions were obtained by Metropolis-Hastings and Gibbs sampling algorithms. The Gompertz function presented lower DIC and better adjustment at different ages and was defined as the best fit. The heritabilities of A, b, and k parameters were moderate (0.32, 0.29, and 0.18, respectively). The genetics correlations were A and b (0.25), A and k (-0.50), and b and k (0.03). The samples of the posterior marginal distributions for the differences between the estimates of the parameters of the Gompertz model, for generation, A, b, k, age at inflexion point (APOI), and weight at inflexion point (WPOI) showed differences in relation to sex, the females are heavier, A, WPOI, and APOI for females were also higher. In conclusion, 15 generations of selection and changes in the environmental conditions altered the growth curve, leaving the quails heavier and with greater WPOI and APOI, decreased growth rate, and increased the birth weight. The curve parameters could be used in a selection index, despite the difficulty in selecting quails with higher rate of growth and adult body weight.

Estudo alométrico em codornas para corte alimentadas com treonina digestível / Allometric study in quails fed with digestible threonine

O objetivo do estudo foi avaliar a alometria da carcaça de codornas de corte nas fases inicial e de crescimento alimentadas com níveis de treonina digestível. O estudo foi composto por dois experimentos, o primeiro para o estudo da fase inicial (7 aos 21 dias) e o segundo para a fase de crescimento (22 aos 42 dias). Foram utilizadas quatro níveis de treonina digestível na dieta em ambos os experimentos. O delineamento experimental adotado para os dois experimentos foi o inteiramente ao acaso com quatro tratamentos e 10 repetições, totalizando 40 unidades experimentais. Foram pesados: asas, dorso, músculo do peito e osso do peito, músculo das pernas e osso das pernas, pele do peito e pernas, gordura do peito e pernas e outros (fáscias, vasos sanguíneos). Foi utilizado o delineamento inteiramente casualizado com quatro níveis nutricionais x dois sexos (4x2), com dez repetições. No estudo alométrico, as codornas machos alimentadas com dieta composta por 0,98% de treonina digestível na fase inicial obtiveram efeito para o crescimento do peito, sendo este crescimento tardio; na fase de crescimento foi obtido efeito para peito em ambos os sexos com a inclusão de 0,72% de treonina digestível na dieta. A inclusão de 0,72% de treonina digestível na dieta de codornas para corte é o recomendado para o efeito tardio na deposição do músculo do peito em ambos os sexos.

The aim of this study was to evaluate the appropriate level of threonine in the diet of quails in their initial period and growing period for the carcass allometric development was studied. This study consisted of two experiments: the first one looks into the initial period (7 to 21 days), and the second one investigates the growing period (22 to 42 days). Four levels of threonine were used in the diet. The experimental design was completely randomized in a factorial arrangement with four treatments and 10 repetitions, totaling 40 experimental units. The dissection of the carcasses was performed in the laboratory of Animal Science Department of the meat of the Federal University of Pelotas, were weighed: wings, back, chest muscle and chest bone, muscle and bone of the legs, chest and legs' skin, breast and legs' fat and others (fascia, blood vessels). In the allometric study, male quails with a diet composed of 0.98% of digestible threonine obtained positive effects for breast growth in the initial period, but this growth is delayed; for 42-day quails of both genders with a diet composed of 0.72% of digestible threonine the breast growth is also delayed. The inclusion of 0.72% digestible threonine quail diet was recommended for late effect on deposition of breast muscle in both gender.