Productive factors associated with pregnancy in beef cows at different ages

Abstract

The objective of this work was to evaluate productive variables that can affect the reproductive performance for odds-ratio, in order to increase or reduce the pregnancy rate in beef cows at different ages. A logistic regression model was used to analyze the response variable “rate of pregnancy”. The productive variables were lactation period, milk production, interval between calving and end of reproductive season, weight, body score, and daily gain. The variables in the regression equation were tested for multicollinearity, and the parameters were evaluated by odds-ratio statistics. Adjusting the lactation period by seven days significantly influenced the pregnancy rate of three-year-old cows, since an extension of seven days increased the pregnancy rate by 27.3%, while a reduction of 7 days decreased it by 21.4%. During the reproductive period, changes in mean daily weight gain was the most consistent variable for pregnancy, with a significant effect on cows of three, four, and five years of age. Reproductive success is a result of different variables that depend on the age of the cow. For adult beef cattle, early calving and adequate weight gain are essential during the reproductive period. For younger categories, a short lactation period is essential.