Age at First Calving and its Relationship with Efficiency Indicators in Nelore Cows in a Grazing System in the Bolivian Tropics

Abstract

Age at first calving is a factor attend for female cattle efficiency. The objective of this study was to evaluate the age at first calving and its relationship with productive efficiency indicators in Nelore cows in a grazing system of the Bolivian tropics. For the research, retrospective data corresponding to the period between 2005 and 2019 were used. The data belong to the Cooperativa Agropecuaria Integral San Juan de Yapacaní, Santa Cruz - Bolivia. The data corresponding to 259 Nelore breed cows, primiparous and multiparous, with a total of 800 calvings were used. The age at first calving of the cows was 1098 ± 152 days for the total of the cows analyzed. That three groups of cows were found with significant differences (p≤0.05) among them according to age at first calving, where from that differentiation the cows that take longer to reach their first birth (1263 days) have an intermediate longevity (2203 days), the highest live weight, the lowest number of births and the shortest calving interval (440 days). The Accumulated Production showed that the cows of with significant differences (p≤0.05) among them according to age at first calving. In the same way the low age category showed the Calf Index. It is concluded that the age at first birth does not affect longevity, reproductive behavior and the number of births during their life. But when compared with efficiency indicators such as the Accumulated Production and Calf Index, the cows belonging to the low age category were the most efficient.