Desempeño reproductivo de vacas de 1er parto de las razas Angus, Braford, Brangus y Hereford

The purpose of this study is to evaluate the reproductive performance of first-calving cows from Angus, Braford, Brangus, and Hereford breeds. These cows were served for the first time at 18 months of age, preceding the second breeding season under natural grazing conditions. The research took place at 'La Magdalena' farm, owned by Los Tordos SA, situated 17 km away from km. 53 of route no. 31, in the 9th Police Section of the Salto department in Uruguay. The experimental period spanned from days before the first births in March, extending until October, just before the spring service. A total of 77 cows were managed under consistent environmental and management conditions, comprising 25 Angus, 16 Braford, 14 Brangus, and 22 Hereford. Three key variables were recorded: live weight, body condition, and ovarian activity—the determinant of reproductive performance, assessed at three strategic moments. Live weight and body condition were recorded six times to complement reproductive information. The experiment concluded with the final diagnostic of ovarian activity before a new fixed-time artificial insemination protocol. Variance analysis revealed no significant differences in reproductive performance among the studied breeds in this work.