Desenvolvimento e desempenho reprodutivo de vacas primíparas aos 22/24 meses de idade

Abstract

Reproductive performance of primiparous cows at 22/24 months of age ABSTRACT -The objective of this work was to evaluate the feed systems for 70 primiparous beef heifers from the initial gestation period at the age of 13/15 months to the end of the second reproductive period as primiparous cows at 22/24 months of age. The experimental design was fully random with plots subdivided in time considering animals as replicates.The initial mean live weigh was 282 kg and the initial mean body condition was 3.2. The feeding systems were proposed to obtain higher live weight gain at initial (PCIG) or final (PCFG) gestation period: PCIG -pregnant heifers on pearl millet pasture (Pennisetum americanum, L.) during the initial gestation period and on natural pasture at pre-calving period; PCFGpregnant heifers on natural pasture during the initial gestation period and on oat (Avena strigosa Schreb) and annual ryegrass (Lolium multiflorum Lam) pasture at pre-calving period. At initial gestation period, the mean live weight gain of 0.424 kg of PCIG heifers was higher than 0.245 kg of PCFG heifers. In the pre-calving period, PCIG heifers lost weight, 0.303 kg/day and presented BC of 0.77, while PCFG heifers gained 0.901 kg/day and presented BC of 0.37. The weight of 323 kg and body condition of 3.3 of post-calving PCFG heifers were higher than 274 kg and BC of 2.6 of PCIG heifers, respectively. PCFG heifers had calves 4 kg heavier. In the beginning of the second reproduction period, PCFG cows were 35 kg heavier and presented BC of 0.60. The pregnancy rate of 85% of PCFG heifers was higher than 53% of PCIG heifers.Pregnant cows had the highest body condition rate at calving and at the beginning of the second reproduction period, presented higher calving and mating interval and heavier calves.Key Words: body condition, dystocia, calving, live weight, grazing systems IntroduçãoO número de bezerros desmamados em relação ao número de fêmeas do rebanho é fator determinante, direto ou indireto, da rentabilidade na atividade pecuária do Brasil. Altos índices reprodutivos possibilitam ocupar áreas destinadas a vacas não-gestantes e novilhas em crescimento com categorias produtivas, basicamente R. Bras.

Desempenho Ponderal E Reprodutivo No Período Das Águas De Novilhas Primíparas Nelore Com Complemento Proteico Prévio Na Seca

“…Para a obtenção desses resultados, os animais foram submetidos a práticas de alimentação e manejos diferenciados, associados à genética animal, à realização da desmama precoce e, assim, a um acasalamento antecipado. O peso das primíparas ao parto reflete a condição alimentar da vaca durante a gestação, sendo, portanto, uma variável importante para determinar o subsequente desempenho reprodutivo desses animais (28,29) . O manejo nutricional das primíparas deve ser adequado, de modo que os animais apresentem uma condição corporal favorável, propiciando-lhes o retorno da ciclicidade ovariana.…”

Natural and improved natural pastures on the reproductive performance of first-calf beef cows

“…Lobato et al (1998a) also found lower pregnancy rates in first-calf cows presenting higher body weight at the end of the breeding season. According to Pilau & Lobato (2009), the higher body weight associated to the higher body condition score determined pregnancy rate and conception period in the second breeding season of first-calf cows.…”

Different corporal structures determining the effective production of Red Angus primiparous cows at 24 months of age

“…This could be aggravated when the cows are primiparous, and may result in impaired reproductive performance or future development (CERDÓTES et al, 2004). However, the effects under favorable environmental and nutritional conditions have not been verified (PILAU;LOBATO, 2009).…”

“…No differences in weight gain during lactation and calf weight at weaning demonstrated that there were three potential body sizes for calf growth in this productive system. However, the equal performance of the calves may be owing to greater stress of the cow, which tries to produce more milk for the calf based on its requirements (VIEIRA et al, 2005), and undergoing greater stress in adverse environmental conditions (PILAU;LOBATO, 2009). The performance of the calf from birth to weaning is directly related to a combination of factors, such as calf genotype, breeding environment, and maternal ability (VIU et al, 2006).…”