Effects of the weaning age of calves on somatic development and on reproductive performance of beef cows

Abstract

-This study evaluated body development and reproductive performance of beef cows whose calves were submitted to early weaning (76 days of age), or conventional weaning (148 days of age). It was used 141 Braford cows that calved in 2004, 2005, and 2006 to evaluate weight at calving at 76 days, weight at calving at 148 days, weight at the beginning and end of the breeding season, variation of the average daily weight, body condition, pregnancy rate, and calving interval.Dams of calves weaned at 148 days of age showed daily weight gain higher body weight and better body condition at 148 days of age. The weights at the end of breeding season and average weight gain during the breeding season were higher in early weaning cows than in conventional cows. Pregnancy rate of early weaning cows (86.34%) was higher than those submitted to weaning at conventional age (55.45%). Pasture interval was similar among early weaning cows and conventional weaning cows. The best benefit on reducing weaning age in pregnancy rate was in primiparous cows. There was significant interaction between weaning age and the year for calving interval and milk production. The early weaning of calves carried out at 76 days of age allows cows to better weight recovery in the post-weaning and breeding periods, improving their body condition and consequently increasing pregnancy rate regarding to cows whose calves suckled until 148 days of age.

Performance of beef cows of different genetic groups in natural and cultivated pastures

“…The differences in calving weights occurred as a direct result of the feeding system used, where cows with better pre-calving conditions were heavier. Better feeding conditions pre-calving are major determinants of weight at calving for cows and calves (CERDÓTES et al, 2004a), because the greatest nutritional requirements of pregnant cows are concentrated in the final trimester of pregnancy and the first three months of lactation, as this period coincides with the subsequent cow reproduction (VAZ; LOBATO, 2010).…”

“…According to Lobato, (2010), lactating cows do not perform well reproductively and not provide sufficient milk for calf healthy development (RESTLE et al, 2004). These authors emphasize the high nutritional demands of cows, regardless of stage in the reproductive cycle, as there as overlaps of the nutritional demands for maintenance, milk production and reproduction throughout the year, in addition to growth when primiparous.…”

“…The low birth rates in addition to adversely affecting the offtake and productivity indicators of the herds (BERETTA et al, 2002), reduce the possibility of genetic improvement through selection due to low availability of replacement females (VAZ; LOBATO, 2010). The animals are born with their sexual behavior linked to factors related to the genetic load itself, but these factors interact with the environment promoting or inhibiting their reproductive behavior .…”

Minimizing cows’ stress when calves were early weaned using the two-step method with nose flaps

“…As early weaning is done with the objective of advancing the first ovulation in postpartum cows under range conditions (Parfet et al, 1986;Quintans et al, 2009;Vaz and Lobato, 2010), the reduction of cows' stress may contribute positively to reproductive outcomes. Our results showing minimal behavioural responses indicative of stress responses in the cows when the calves were prevented from sucking with the nose flaps may also be relevant for those using temporary sucking restriction regimes to induce ovulation in postpartum cows, as in some cases these involve preventing calves of the same age as in this study from sucking for a short period of time (e.g.…”

“…In this context, suckling managements can be used to stimulate ovulation and consequently early pregnancy rate in beef cows (Quintans et al, 2009 and. In extensive grazing systems in which cows usually have a low body condition after calving due to the high dependence on native pastures, early weaning has been developed as an alternative that provided good results to farmers by advancing postpartum rebreeding and increasing pregnancy rates (Williams, 1990;Arthington and Kaimbacher, 2003;de Castro et al, 2006;Vaz and Lobato, 2010).…”