PRECOCITY OF CALVING SEASON IN THE PRODUCTIVE EFFICIENCY OF PRIMIPAROUS COWS AT 24 MONTHS OF AGE

Abstract

The aim was to evaluate the effects of two calving periods, during the calving season (early: September; and late: October), in the efficiency of 54 Red Angus primiparous cows at 24 months of age. Over the pre-parturition and parturition periods, the cows were kept in natural and cultivated pastures of Lotus corniculatus and Lolium multiflorum, respectively. Fixed-time artificial insemination was used, with two protocols in a interval of 30-day. Pregnancy diagnosis was performed 30 days after each protocol. Calves from early calving cows presented larger weight daily gain, and were heavier at weaning when compared to later calving cows, resulting in higher cow-calf gains during the lactation (0.721±0.030 e 0.699±0.032 kg). The reproductive performance was higher for the early calving cows in both synchronizations, and in the total pregnancy rate (86.2 and 52%). Early calving cows had a higher calf production rate (161.5±3.2 e 92.5±3.5 kg), calf/kg of cow at weaning (40.9±0.97 e 23.7±1.04 kg), and productive efficiency in the calving (34.3±1.25 e 20.8±1.35 kg). Early calving cows are more efficient in production of calves kg/cows kg in the calving and in the weaning, and when associated the kg produced and the subsequent pregnancy, presented a higher calf production rate.
Keywords: weight gain; index of calf production, pregnancy; Red Angus.