The reproductive performance of beef cows of different ages with calves weaned at three or seven months
Anim Reprod, vol.4, n1, p.42-45, 2007
The aim of this study was to evaluate the reproductive performance of beef cows in different age groups, with the calves weaned at three (early weaning) or seven months (conventional weaning). The study was based on data gleaned from 1,868 cows from 3 to 11 years old (British breeds and cross-breeds) on a farm located in Cristal, a South Brazilian town. During the experiment, the animals were raised only on natural pasture. The mating season ranged from mid-November to mid-February (11/19 to 02/19). After pregnancy diagnosis, information was analyzed according to the age of the cow (A3 to A11) and to the weaning procedure, early (EW) or conventional (CW). A chisquare test was performed to evaluate the reproductive performance of the cows in each age group (PRA3, PRA4, PRA5,..., PRA11), as well as the reproductive performance of cows submitted to early weaning (PREW) and conventional weaning (PRCW). Pregnancy rates were higher for EW only, for cows 3 and 4 years old (A3 and A4, 84.3% and 95.0%, respectively; P < 0.01). There was no statistical difference in the PREW and PRCW of cows mating between 5 and 11 years old. Cows that were 6 years of age reached the highest pregnancy rate (97.4%). The PRT (pregnancy rates that did not consider the age) was 88.7% and 82.0% for the EW and CW, respectively (P < 0.01). Therefore, the age of weaning had a strong influence on the reproductive performance evaluated by pregnancy rate, especially on animals between 3 and 4 years old.
weaning age, pregnancy rate, bovine