The objective of this experiment was to evaluate the performance of Charolais (C), Nellore (N), CN and NC crossbred cows, kept on native pasture, supplemented with rice bran and weaned at 42 or 63 days, or not supplemented and weaned of 63 days. Cow age ranged from 3 to 12 years and was classified into four groups, first calf, young, adult and old cows. Average daily weight gain (ADG) from calving to 63 days postpartum was higher for supplemented cows. Cows weaned at 42 days showed higher weight difference (61.5 kg) from calving to pregnancy diagnostic than the not supplemented cows (45.7 kg), and did not differ from the supplement cows weaned at 63 days (57.8 kg). From the end of the mating season to the pregnancy diagnostic the CN crossbred cows showed higher ADG (860 g) than the C (552 g) and N (648 g) and did not differ from the NC (670 g). Nellore cows were lighter than the other genetic groups at all periods evaluated. First calf and old cows lost weight, while young and adult cows showed light weight gain from calving to weaning. Supplemented cows weaned at 42 days showed lower calving interval (CI) than those weaned at 63 days (367 vs 384 days), however, did not differ in calving rate, respectively, 72.0 and 72.2%. For 63 days weaned cows, supplementation did not alter CI, but resulted in significant increase in calving rate (72.2 vs 53.7%). Adult and old cows weaned at 42 days showed shorter CI than one year, 356 and 353 days, respectively, displayed higher weight and body condition at gestation diagnostic and higher calving rate, respectively, 80.0 and 76.3 %, versus 41.4 and 57.5%, observed for first calf and young cows.
Bos indicus; Bos taurus; crossbreeding; early weaning; reproduction
