Abstract The aim of this study was to evaluate the effects of conception weight and gestational weight gain on performance and productive efficiency in beef cows and their calves. Eighty-eight primiparous, three-year old Braford females were used, divided according to weight at conception and gestational performance (High and Low): cows with a low conception weight and low gestational weight gain (LL), cows with low conception weight and high gestational weight gain (LH), cows with high conception weight and low gestational weight gain (HL), and cows with high conception weight and high gestational weight gain (HH). At calving, HH cows were heavier than LH and HL and these were heavier than LL cows. Male calves born to HH cows were superior in body weight to those born to LL cows at 150, 210 and 365 days. Female calves born to HH, HL or LH cows were superior to those born to LL cows in pregnancy at 14 months of age. The LL and HL cows were more efficient in calf production. Actual fertility was influenced by the nutritional level of the herd, where HH cows were superior than LL cows. Better cow herd nutrition increases the development and performance of the progeny.

Abstract The aim of this study was to evaluate the influence of two sub-periods of the calving season and two cow maturity stages on the efficiency of beef cows and their calves. A total of 159 cow-calf pairs were divided by calving time (early or late) within the calving season and maturity stage (young or adult). Calves were weaned at 42 or 63 days after birth and evaluated until 210 days of age. Cows and calves had their development examined based on their weight and body condition score at calving, at weaning, and at 210 days. Reproductive performance was evaluated on the basis of time to become pregnant again. Milk yield was assessed by the direct method on three occasions spaced 21 days apart. Adult cows were heavier than young cows, at calving (398.5 vs 327.5 kg, respectively), weaning (397.3 vs 324.1 kg, respectively) at the end breeding season (424.1 vs 342.1 kg, respectively). Reproductive performance was influenced by calving time. Adult cows had higher pregnancy rates (83.75 and 69.17%, for early and for late calving, respectively) than young cows (57.03 and 35.01% for early and for late-calving, respectively). Calves from early-calving young cows weighed 158.8 kg at 210 days of age vs. 123.7 kg for those born from late-calving adult cows. However, late-calving cows produced 10.7% more milk than those that calved early in the season (227.0 vs 205.0 liters, respectively). Early calving associated with non-requirement of growth determine higher productivity efficiency in beef cows.

Objetivou-se com esse estudo avaliar o risco da terminação em confinamento de novilhos jovens (22,8 meses) ou superjovens (15,2 meses), utilizando ou não correlação entre variáveis de entrada aleatórias (dados coletados de 2004 a 2010) na simulação do indicador financeiro Valor Presente Líquido (VPL). Os animais foram alimentados com dieta contendo relação volumoso:concentrado de 60:40 por 34 e 143 dias, respectivamente, até atingirem peso de abate previamente estabelecido de 430 kg. Para simulação do VPL, utilizou-se o tipo de amostragem Latin Hypercube, com 2000 interações. Procedeu-se análise de dominância estocástica, teste de diferenças entre pares de curvas de distribuições acumuladas e análise de sensibilidade. A simulação do VPL com uso da correlação resultou na melhor opção para estimativa do risco. A terminação de novilhos superjovens foi alternativa de investimento mais viável, comparativamente aos jovens (VPL ≥ 0 de 80,4 vs. 62,3% na simulação com correlação, respectivamente). A análise de sensibilidade determinou os seguintes itens de maior impacto na estimativa do VPL: cotações do boi gordo e magro, pesos final e inicial, custos com dieta, taxa mínima de atratividade e consumo da dieta.

The objective of this study was to evaluate the risk of feedlot finishing of steers (22.8 months) and young steers (15.2 months), using or not a correlation between the random input variables (data collected from 2004 to 2010) in the simulation of the Net Present Value (NPV) financial indicator. The animals were fed a diet containing roughage:concentrate ratio of 60:40 for 34 and 143 days, respectively, until they had reached a predetermined slaughter weight of 430 kg. For the NPV simulation, Latin Hypercube sampling was used, with 2000 interactions. The stochastic dominance analysis, test of differences between pairs of curves of cumulative distributions and sensitivity analysis were carried out. The NPV simulation using the correlation resulted in the best option for risk estimate. The confinement of young steers was the alternative of investment most viable than confinement of steers (NPV ≥ 0 of 80.4 vs. 62.3% in the simulation with correlation, respectively). Sensitivity analysis determined the following items had the greatest impact on the estimate of NPV: prices of fat and thin cattle, initial and final weights, diet costs, minimum rate of attractiveness and diet intake.