Nutritional levels in rearing, gestation and postpartum on the performance of primiparous

• Autor(a) principal: Lobato, José Fernando Piva
• Data de Publicação: 2024
• Outros Autores: Rosa, Antonio Augusto Galarza, Pacheco, Paulo Santana, Sá, Haylleen Aparecida Menezes Oliveira de, Vaz, Ricardo Zambarda
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Semina. Ciências Agrárias (Online)
• DOI: 10.5433/1679-0359.2023v44n6p2113
• Texto Completo: https://ojs.uel.br/revistas/uel/index.php/semagrarias/article/view/48204
• topic: Stocking rate; Natural pastures; Improved natural pastures; Pregnancy rate.; Carga animal; Pastagem natural; Pastagem natural melhorada; Prenhez.

This study evaluated the reproductive performance of 36-month-old Hereford primiparous cows(n = 119) fed different nutritional levels during rearing and pre-mating. Nutritional levels were based on twostocking rates (SR) and the use or not of improved pastures. Heifers grazed on natural pastures duringrearing at two different SRs (0.8 and 0.6 animal units [AU] per ha). Before the first mating period, eachgroup was allocated either to natural or improved natural pastures at a single SR (0.7 AU ha -1 ). The betterpre-mating live performance of heifers grazing on improved pastures, independently of SR during rearing,was not maintained during gestation, as all heifers achieved similar body weight (BW) and body conditionscore (BCS) at calving. After calving, cows were allocated to natural or improved natural pastures,independently of the previous feeding system. Except at calving, cows grazing on improved natural pasturesshowed higher BW, BCS, and BW change until the end of the mating period than those grazing on naturalpastures. The higher nutritional levels supplied by improved natural pastures promoted higher pregnancyrates (44.3%) than natural pastures (13.8%). Pregnancy rate increased according to BW range (very light,light, medium, or heavy), with observed values of 0.0, 18.8, 21.2, and 88.0%, respectively. Cows with BCSlower than 2.6 did not conceive, whereas a 48.1% pregnancy rate was observed in cows with 2.6-3.4 BCSand a 100% pregnancy rate in cows with 3.5 or higher BCS. Grazing on improved natural pastures during thepost-calving period promotes higher body weight and body condition scores in primiparous cows, resultingin higher pregnancy rates.