Análise genética da probabilidade diária de postura em três linhagens de codornas

Abstract

The objective of this work was to estimate genetic and residual (co)variance components as well as to investigate the existence of the genotype environment interaction, in three lines of laying quails under two feeding types: high and low energy. The posture control was daily accomplished until to the 90th day starting from the first egg laying in each line. The daily egg production data were used to fit a polynomial regression for each animal, using the method of Linear Models Generalized, using the software GLIM 4.0, and assuming that it is a binomial distribution and logit link function. For the genetic analyses the parameters of the individual production curves were considered as biological traits under a multi-trait animal model. The residual and genetic variance components were estimated using the software MTGSAM. In two-trait analyzes the heritability estimative for b0 were 0.031, 0.009 and 0.387, and for b1: 0.091, 0.763 and 0.443 for lines 1, 2 and 3, respectively. The genetic correlation between b0 and b1 was 0.88; -0.113 and -0.984 for the lines 1, 2 and 3, respectively. To produce genetic improvement, the selection should be based on the b1 in lines 2 and 3, and due to genetic correlation among the parameters, in those two lines, to be negative; it will also have improvement genetic in the parameter b0. Besides, these results indicate differentiation between lines that can be explored in genetic improvement programs. In the four-trait analyzes, which the performance in different environments is considered as different traits, the heritability estimated for b0 in the environment 1, for lines 1, 2 and 3 were, respectively: 0.003, 0.002 and 0.282, and for b1: 0.065, 0.034 and 0.379; for b0 in the environment 2: 0.003, 0.004 and 0.442 and for b1 0.048, 0.514 and 0.502. In a general way the heritability was higher in the environment 2, indicating that a selection program would be more efficient if performed in this environment. The genetic correlations between the environments for b0 were: 0.255, 0.234 and 0.987 and for b1 0.408, 0.294 and 0.928 for lines 1, 2 and 3, respectively. These results indicated a strong genotype by environment interaction in lines 1 and 2. In line 3 the selection can be practiced in the environment of higher energy and the progenies reared in other environment, without damages in the expression of the eggs production curve. Already for lines 1 and 2 the progeny should be reared in the same environment that the parents were selected.