Eficiência biológica de um rebanho de cria Charolês de diferentes estruturas corporais.

Abstract

With the development of the agricultural sector and the growth of the agriculture area, occurred reductions in pasture areas, requiring greater efficiency of the livestock sector for the activity to continue. In this way, the animal size must be considered, since it is related to the cost of production, the maturation rate, the reproductive efficiency and, more important, the economic efficiency of the production systems. This study aimed to evaluate the production, reproductive performance and productive efficiency of predominantly Charolais cows and their calves (Pure, % C, % N) according to their body size at calving. Sixty-three cow:calf pairs were used and classified into the groups Light (331.4±5.8), Moderate (385.9±5.3) and Heavy (424.3±6.2). The classes were formed with half standard deviation above or below the average weight of cows at calving. For each pair, the body weight was evaluated at calving, at weaning (63 days), at the beginning and at end of the reproductive period, and calves at nine months. Pregnancy rates were similar (P>0.05) between weight groups. The calves did not differ (P>0.05) in weight and body weight gain from calving until 210 days. The calves from Heavy cows had greater weight variations from 210 days to 270 days if compared to Light cows. The calf production rate (kg calf/cow kept in herds) did not differ. However, upon relating it to the weight of the cows at 210 days, Light cows were more productive (P<0.05), with a 11.28 and 13.02% increase in calf production when compared to Moderate and Heavy cows, respectively. Light cows were more efficient at calving and at 210 days. Through simulations, there were more kilos eligible for sale in herds of Light cows (53.085 kg) compared to Moderate and Heavy cows (52.310 and 52.870 kg, respectively), while maintaining the structures of the herd constant. The size of the Charolais cow does not influence the weight of calves from calving until seven months of age, nor their reproductive performance provided they weaned early. The need for area for the maintenance of the pair cow:calf increases with the increase in the weight of cows. In herds with smaller cows, higher numbers of arrays and a higher production of weight for sale are observed when compared to Moderate and Heavy cows. Light cows are the most efficient at calving and at 210 days.