Reproduction efficiency of Holstein x Gir crossbred animals in Brazilian dairy farms were evaluated using data provided by the Brazilian Association of Girolando. A total of 2,600 records of age at first calving (IPP) and 3,763 records of calving intervals (IDP) were analyzed using the SAS® GLM procedure. Estimates of genetics effects: additive difference between Holstein and Gir breeds, dominance and additive x additive epistatic effects were obtained by regression models including genetic groups to model the performance of crossbred groups. The genetic group 1/2 showed better performance: lower averages for IPP and IDP than the other groups. It was observed a trend of increasing IDP as the proportion of Holstein genes increased. The dominance effect influenced significantly both traits, while the additive x additive epistatic effects significantly influenced only IPP. The results indicated that loss of favorable epistatic interactions contributed to high IPP average in the 5/8 group.
crossbreeding; epistatic effects; Girolando; heterosis; reproductive efficiency
