The experiment was run at the Agronomic Experimental Station of the Federal University of Rio Grande do Sul, located in the district of Eldorado do Sul, Brazil. The objective of the study was to evaluate the effect of the date of early (01/05/99) or conventional (03/26/99) weaning on the reproductive performance of multiparous beef cows during two mating seasons, 98/99, and the subsequent, 99/00. Fifty cows had their calves weaned with an average age of 91 days old and a minimum liveweight of 70 kg (early weaning = EW), and 43 cows had calves weaned with an average age of 170 days old and mean liveweight of 131.2 kg (conventional weaning = CW). The mating periods were from 12/01/98 to 02/26/99 and from 12/06/99 to 02/28/00. Cows of EW had higher daily liveweight gains and better body condition (BC) than CW during the first breeding season (0.828 kg x 0.549 kg; 2.4 x 2.0; P<0.05). The pregnancy rate in 1999 was 40.0% x 11.1% and in 2000 it was 51.4% x 20.0% for EW and CW, respectively. There was no difference in the calving intervals. The pregnancy rate at first mating was lower than the expected, probably due to the low BC at beginning of the mating season and to the low recovery during the mating period. The EW improved cows BC during the first mating, making possible significantly better reproductive rates than the CW.
beef cows; body condition; pregnancy rate; reproductive performance; weaning age
