age at ﬁrst calving, weight gain, crosses, genotype-environment interaction, Amazonia
The objective of the present work was to evaluate the growth pattern during the first gestation of heifers crossed with Brahman father and different maternal genotype, in the Ecuadorian Amazon. Retrospective data of 2304 individual weights of 48 dairy cows were used. With this, the dynamic behavior of the body weight of four genotypes was evaluated: Brahman x Gyr (Gyr) (n=12), Brahman x Brown Swiss (BS) (n=12), Brahman x Jersey (J) (n=12) y Brahman x Sahiwal (S) (n=12) belonging to the dairy herd Centro de Investigación, Posgrado y Conservación de la Biodiversidad Amazónica (CIPCA) – Ecuador. The differences between genotypes in body weight at pregnancy and at first birth were not statistically significant. Differences in age at the first pregnancy were observed, with the highest precocity at crossing with Brown Swiss mother and the lower precocity at crosses with Gyr and Sahiwal. The females produced by crossing with Jersey showed intermediate behavior. It was observed that, during their first gestation, F1 heifers with Brahman father and different maternal genotype have a similar growth pattern under the conditions of the Ecuadorian Amazon, interpretable response in terms of negative genotype-environment interaction.