Efeito de fatores genéticos e ambientais sobre a produção de novilhas leiteiras

Abstract

Even though Brazil is the third largest milk producer in the world, it has a heterogeneous production, ranging from small to large producers and whit a deficiency in technical assistance to optimize production. Milk is also economically and socially important to the population because of its importance in human nutrition. The management and care of replacement heifers directly influence the productivity of these animals not only in the first lactation , but also in the subsequent ones. Therefore, heifer management decisions can have a major effect on the immediate and future profitability of the property. For this dairy heifers on a commercial property and determine the economic value of each oh these factors. Data where collected in a commercial property located in the city of Patrocínio-MG, where zootechnical data of 54 heifers. Qualitative variables (father, maternal grandfather, colostrum consumed, use of antibiotic in the first day of life; application of prostaglandin for induction of heat, application of prostaglandin for resynchronization, use of progesterone implant for resynchronization, occurrence of retention of placenta and/or abortion, induction of lactation) where teste individually by analysis of variance, the F test being used to compare the variance estimates for each treatment. When significance was detected at 5%, the Tukey teste was applied to compare the means. Quantitative variables (weight at 90 days, average daily gain at 90 days and age at first coverage) where analyzed individually by simple linear regression, with significance teste by the T statistic. When significance was detected at 5%, model estimates provided the effect of the variables on production. Among these variables, those that were influenced were the application of antibiotics, placental retention, induction to lactation and age to coverage because they are factors that directly interfere in the reproductive efficiency of heifers. Among the factors that had an effect on the production at the first lactation of the heifers and the difference in the milk prescription were the use of antibiotics (- R$ 2,381.21), age at coverage (-R$ 299.85), the occurrence of retention of placenta with (-R$ 6,841.16) or without abortion (-R$ 1,060.96) and induction of lactation (-R$ 5,043.11). Knowing the productive and economic implications of each of these items, the producer has subsidies to know how much he can spend on management that avoids such losses, in order to improve the result and viability of production.