Fatores determinantes do desempenho reprodutivo de vacas Nelore na região dos Cerrados do Brasil Central

Self Cite

-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.Key Words: body condition, Brangus, improved pastures, natural pastures, pregnancy rate, weights Sistemas forrageiros pré e pós-parto e desempenho reprodutivo de vacas primíparasRESUMO -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 pós-parto (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%), respectivame...

Section: Resultsmentioning

confidence: 99%

“…In this context, high pregnancy rates are difficult to obtain in primiparous cows, and therefore they should be managed separately from mature cows, and be fed at higher nutritional levels. According to Vieira et al (2005b), first-and second-calf cows with calves present the lowest pregnancy rates in cow herds.…”

Section: Introductionmentioning

confidence: 99%

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

Lobato

Menegaz

Pereira³

2010

Self Cite

“…O terço final da gestação em fêmeas bovinas é o período de maior restrição alimentar Vieira et al, 2005). Para a novilha prenhe aos 13/15 meses de idade manter-se em gestação, parir em condições de criar bem o bezerro e conceber no período reprodutivo subseqüente, deve ter bom ganho de peso durante a gestação.…”

unclassified

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

Pilau

Lobato

2009

Self Cite

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.

“…Vieira et al (2005), working with five 20-day calving subseasons, found that pregnancy rates were higher than 90% when calvings occurred during the first sub-season (from August 12 th to September 1 st ) and 79.9% for calving occurring during the last sub-season (from October 31 st to November 20 th ). This demonstrates that calving date and season strongly influence reproductive performance.…”

Section: Resultsmentioning

confidence: 99%

Calving sub-season and reproductive efficiency of beef cows

Reinher

Barcellos

Peripolli³

et al. 2010

1 st to 20 th ). Calving sub-season significantly influenced pregnancy rate. Cows which calved in the initial sub-season showed higher pregnancy rates than cows which calved from the fourth calving sub-season. However this difference did not occur in 1999 and in 2007 since calving rates did not statistically differ among the five sub-seasons. In 1998 and 2004, calving rates were lower and the effects of calving sub-season on pregnancy rates were higher, possibly due to climate variations.In general, pregnancy rate decreases as calving occurs later in the year, particularly in years when the weather adversely affects pasture growth.