Abstract
ABSTRACT: This study sought to estimate (co)variance and genetic parameters for birth weight (BWT) and weaning weight (WWT) in Santa Ines sheep. A total of 2,111 records were obtained from EMBRAPA/CPATC experimental herds, dating from the years 1998 to 2008. (Co)variance parameters were obtained through a two-trait analysis with the Gibbs sampling algorithm using the MTGSAM program. The mixed model included the environmental effects of sex, contemporary group and type of birth, in addition to residual, direct and maternal additive effects. Mean estimates of direct heritability for BWT and WWT were 0.25 and 0.09, respectively. Mean estimates of maternal heritability were 0.34 for BWT and 0.24 for WWT. The genetic correlation between BWT and WWT was 0.14. The results suggest that breeding Santa Ines sheep for meat production must take into consideration direct and maternal additive genetic effects.
Highlights
In Brazil, sheep meat production has been expanding due to the increasing consumption of sheep meat
Weight at specific ages is associated with different traits that are generally correlated with one another; this factor makes it critical to know the magnitude and direction of such correlations, given that the selection of one trait could promote changes in other traits. Growth traits, such as birth weight and weaning weight, and the influence of maternal effects are important for determining the economic efficiency of any sheep production system (SOUSA, 1999)
The Markov errors were low for weaning weight (WWT) (Table 2), they were greater than those observed for birth weight (BWT)
Summary
In Brazil, sheep meat production has been expanding due to the increasing consumption of sheep meat. Body weight, measured throughout the growth period, is the most important piece of information for the genetic evaluation and selection of sheep for meat production. Weight at specific ages is associated with different traits that are generally correlated with one another; this factor makes it critical to know the magnitude and direction of such correlations, given that the selection of one trait could promote changes in other traits. Growth traits, such as birth weight and weaning weight, and the influence of maternal effects are important for determining the economic efficiency of any sheep production system (SOUSA, 1999). Genetic potential can be improved by using genetic evaluations for traits related to growth and subsequently selecting superior animals genetically and there is little information about it
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