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 (GP C) and dam trait (GP D). Genetic parameters were estimated by the restricted maximum likelihood method (REML). Four alternative animal models were tested in single trait analyses of GP C and GP D, 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 GP C and BW and between GL C and W12. Direct heritabilities of GP C varied from 0.22 to 0.41 and of GP D from 0.04 to 0.07. Genetic correlation between GP C and BW was 0.65 and between GP C 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.
beef cattle; body weight at birth; body weight at 12 months of age; genetic correlations; heritability
