Effect of the age at first calving and nutritional management on longevity and productivity in cow-calf systems

Abstract

The age at first calving indicates the beginning of the productive life of dams, and it is related with their longevity. The objectives of this study were: a) to evaluate the productive efficiency at first weaning of heifers reared to obtain their first calving at 24 or 36 month of age; b) to evaluate the age at first calving and differential nutritional strategies on cows survival. The work was carried out at the Instituto de Investigación Animal del Chaco Semiárido, Leales, Tucumán. The treatments were defined by combining the age of first calving (24 and 36 months) and nutritional management: G1) first calving at 36 months and supplementation; G2) first calving at 36 months without supplementation; G3) first calving at 24 months and supplementation; G4) first calving at 24 months without supplementation. The survival analysis was performed using the Kaplan and Meier estimator and the Cox regression. The results show that the probability of overall survival until the fourth weaning was 0.41, 0.35, 0.38 and 0.18 for G1, G2, G3 and G4, respectively (log-rank, P <0.01). Group 4 was the one that showed the lowest cumulative production until the fourth weaning. It is concluded that advancing/anticipating the calving age is not efficient in pure pastoral systems based on natural pastures or implanted megathermal grasses.