R. Bras. Zootec.01/Jun/2011;40(6):1211-6.
Genetic analysis of gestation period in a Canchim beef cattle herd: estimation of genetic parameters and choice among alternative animal models
DOI: 10.1590/S1516-35982011000600008
The objectives in this study were to compare alternative animal models for analysis of gestation period and verify if this trait has enough genetic variability to be included in selection programs, by using heritability estimates and genetic correlations with body weights at birth (BW) and at 12 months of age (W12), in a Canchim herd. Gestations of 2,889 calves, weight of 8,506 animals at birth and 6,372 animals at 12 months of age were analyzed. Gestation period was studied as calf (GPC) and dam trait (GPD). Genetic parameters were estimated by the restricted maximum likelihood method (REML). Four alternative animal models were tested in single trait analyses of GPC and GPD, considering fixed effects and combinations of three random effects. The likelihood ratio test was used to compare the models. Two-trait analyses were realized between GPC and BW and between GLC and W12. Direct heritabilities of GPC varied from 0.22 to 0.41 and of GPD from 0.04 to 0.07. Genetic correlation between GPC and BW was 0.65 and between GPC and W12 was 0.01. It is conclude that GP should be studied as calf trait. The model with only direct additive effects and maternal permanent environmental may be used to genetic analysis of this trait, and this trait may be used as an auxiliary selection criterion.