Suplementação energética pré-acasalamento aos 13/15 meses de idade para novilhas de corte: desenvolvimento e desempenho reprodutivo

Abstract

RESUMO -Avaliou-se o efeito da suplementação pré-acasalamento no desempenho reprodutivo de novilhas de corte aos 13/15 meses de idade. Foram utilizadas 89 novilhas com média de 12 meses de idade e peso corporal (PC) médio inicial de 242 kg, provenientes de três rebanhos (novilhas Aberdeen Angus das Fazendas Santa Cecília e Capitão Rodrigo e novilhas mestiças Aberdeen Angus) submetidas a regime alimentar exclusivamente em pastejo ou com suplementação a pasto com grão de milho moído. As novilhas foram agrupadas dentro dos regimes alimentares considerando o peso inicial e o rebanho.O suplemento foi fornecido diariamente na proporção de 0,7% do peso corporal por 29 dias em pastagem de aveia (Avena strigosa Schreb) e azevém (Lolium multiflorum Lam) e 19 dias em pastagem natural. O pastejo foi contínuo com taxa de lotação variável. As variáveis analisadas foram: peso corporal, condição corporal, ganho de peso médio diário, ganho de condição corporal, porcentagem de novilhas púberes, taxa de prenhez e ordem de concepção. Não houve interação regimes alimentares × rebanhos. Durante o pré-acasalamento, o maior ganho médio diário das novilhas sob suplementação foi maior (0,800 kg) que o daquelas sem suplementação (0,658 kg). No período reprodutivo, as novilhas perderam peso, média de -0,104 kg/dia. O peso corporal e a condição corporal não diferiram ao início do período reprodutivo, média de 277 kg e 3,6 pontos, respectivamente. As novilhas sob suplementação apresentaram maior PNP (por extenso) (78%) e maior taxa de prenhez (47%). Houve interação rebanho × período para peso corporal. A variação no peso vivo foi quadrática entre os três rebanhos. O peso corporal das novilhas mestiças foi sempre superior ao das Aberdeen Angus do rebanho Santa Cecília.As novilhas Aberdeen Angus do rebanho Capitão Rodrigo tiveram maior percentagem de novilhas púberes (80%) e taxa de prenhez (48%). A suplementação energética por 48 dias pré-acasalamento proporciona maior taxa de prenhez em novilhas de corte aos 13/15 meses de idade.Palavras-chave: condição corporal, desempenho, pastagem cultivada, pastagem nativa, prenhez Pre-mating energetic supplementation at 13/15 months of age for beef heifers: Development and reproductive performance ABSTRACT -The effect was assessed of pre-mating supplementary feeding on the reproductive performance of 13-15 month old beef heifers. Eighty-nine heifers were used with a mean age of 12 months and mean body weight (BW) of 242 kg from three herds Aberdeen Angus heifers from the Santa Cecilia and Capitao Rodrigo ranches and crossbred Aberdeen Angus heifers) in a feeding system of only grazing pasture or supplemented heifers on pasture with milled corn grain. The supplement was offered daily at the proportion of 0.7% of the BW for 29 days on Oats (Avena strigosa Schreb) and annual Ryegrass (Lolium multiflorum Lam) cultivated pastures and 19 days on natural pasture. The grazing was continuous with variable stocking rate. The variables analyzed were: body weight, body condition, average daily live weight gain, bod...

Development and reproductive performance of Hereford heifers of different frame sizes up to mating at 14-15 months of age

“…Other authors, working with heifers of the same age and fed similar diets, obtained lower pregnancy rates than the present study; however, the body weights of their heifers at the start of breeding season were lower, also due to lower weaning weights (Rocha and Lobato, 2002;Pilau et al, 2005;Azambuja et al, 2008;Pilau and Lobato, 2009).…”

“…At the end of the cycle, already in end December, and January, the ryegrass stubble presented poor quality, CP of 9.8% and 4.5%, respectively, associated to the worst total digestible nutrients values in the same months, subtracted the possibility of expressing better results. Probably, the offering of a supplement as supported by Pilau and Lobato (2009) in this poor-quality period of the pasture on offer should give better answers.…”

“…In intensive systems, the assurance of more food is strongly necessary to get effective results, because it is impossible to be safe based only on pastures, improved or natural, and expected normal rainfall and temperatures. This was previously recommended by Pilau and Lobato (2009), based on the gains observed in heifers supplemented in this period. More intensive systems require the guarantee of extra food supply to avoid any unexpected hard climate effects, for which they were not prepared in this situation.…”

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

“…However, cows managed on improved pastures presented 100 and 93.1% pregnancy rates (P>0.05). Working with cows with low body weights and body condition scores and managed for 60 days post-calving on improved pastures, Polli & Lobato (1985) obtained higher weight gain (634 vs. -10 g/day) as compared to those maintained on natural pastures; however, the obtained pregnancy rates were not economically justifiable (21.7 vs. 0.0%, respectively).…”

“…Ferrell (1982 also observed weight losses in heifers moved to a lower nutritional level system. But, Pilau & Lobato (2009) used supplementation to promote a better adjustment in this period. The observed body weight change was associated to the higher energy requirement for lactation of growing primiparous cows (NRC, 1996;Freetly, 1999) and to forage availability, which was much lower than the required 2,500 kg DM/ha (Simeone & Lobato, 1996;Pötter & Lobato, 2004).…”