Pre- and post-calving forage systems and reproductive performance of primiparous cows

Abstract

Durante os períodos pré e pós-parto, foi avaliada a influência de sistemas forrageiros no desempenho reprodutivo de vacas primíparas: pastagem natural nos períodos pré e pós-parto; pastagem natural no pré-parto e pastagem melhorada no pós-parto; pastagem melhorada no pré-parto e pastagem natural no pós-parto; pastagem melhorada nos períodos pré e pós-parto. Os menores pesos e condições corporais foram observados nas vacas mantidas em pastagem natural no pré-parto, (384,3 kg e 3,31; 391,4 kg e 3,60), seguidas daquelas em pastagem melhorada no pré-parto e natural no pósparto (424,4 kg e 3,60); e, por ultimo, das vacas em pastagem melhorada no pré e pós- parto (421,2 kg e 3,59). As vacas em pastagem melhorada no pré e pós-parto tiveram maior peso e condição corporal ao início do acasalamento (442,1 kg e 3,76), maior taxa de prenhez (82,3%) e emprenharam mais cedo. Os sistemas com pastagem natural no pré-parto e melhorada no pós-parto e aquele com pastagem melhorada no pré-parto e natural no pós-parto não diferiram quanto a peso ao início do acasalamento (417,2 e 409,8 kg) e taxa de prenhez (65,8 e 62,8%), respectivamente. Entretanto, as vacas em pastagem natural no pré-parto e melhorada no pós-parto emprenharam mais cedo. As vacas mantidas em pastagem natural tiveram o menor peso ao início do acasalamento (391,2 kg), a menor taxa de prenhez (52,7%) e emprenharam mais tarde. Pastagens melhoradas no pré e pós-parto melhoraram os pesos e as condições corporais ao parto e ao início da reprodução, possibilitando alto desempenho reprodutivo.

During pre and post calving periods, it was evaluated the influence of the following forage systems on reproductive performance of primiparous cows: natural pasture during pre and post-calving periods; natural pastures during pre-calving period and improved pastures during post-calving period; improved pastures during pre-calving and natural pasture during post-calving; improved pasture during pre- and post-calving periods. The lowest body weights and body condition scores were observed on cows kept on natural pastures pre-calving (384.3 kg and 3.31; 391.4 kg and 3.60), followed by those on improved pastures during pre-calving and on natural pasture during post-calving period (424.4 kg and 3.60), finally, cows on improved pasture during pre- and post-calving period (421.2 kg and 3.59). Cows on improved pastures pre and post-calving showed higher body weight and body condition score in the beginning of the breeding season (442.1 kg and 3.76), higher pregnancy rate (82.3%) and they conceived earlier. Natural system during pre-calving and improved on post-calving and that with improved pasture in pre-calving and natural in post-calving did not differ on weight at the beginning of breeding season (417.2 and 409.8 kg) and on pregnancy rate (65.8 and 62.8%), respectively. However, cows on natural pasture in pre-calving and on improved pasture in post-calving conceived earlier. Cows on natural pastures showed lower weight in the beginning of breeding season (391.2 kg), the lowest pregnancy rate (52.7%), and they conceived later. Cows maintained on improved pastures pre- and post-calving improved weight and body condition score at calving and beginning of the breeding season making high reproductive performance possible.