Abstract
The aim was to evaluate the association between growth, carcass and visual scores traits with precocious calving in Nellore cattle. Birth weight (BW), weight at 120, 210, 365 and 450 days of age, pre and post-weaning average daily gain, rib eye area, backfat thickness (BF), rump fat thickness and visual scores obtained at 18 months were used for the analysis. Records from 700 females born between 2009 and 2015, exposed to mating starting at 11 months of age were analyzed. Discriminant analyzes were performed with the software Statistica. BW and BF showed the highest (P>0.01) discrimination value for early heifer pregnancy (EP). Extreme intrauterine growth retardation can result in slower growth, which reflects in the worst reproductive performance, confirmed by the variation in BW between precocious and conventional heifers. The results also demonstrate that the level of body fat affects begin of puberty. Bone structure, musculature, depth, tail insertion and rump scores presented the highest discrimination value for EP. These traits can be used as selection tools to improve sexual precocity in female Nellore cattle. The results obtained in this study would support farmers to guide the heifer management and decisions in order to enhance the EP.
Highlights
The beef cattle economic profitability is directly related to reproductive efficiency and age at puberty, since reproductive traits determine the number of calves available for market (Baldi et al 2008)
Reproductive and carcass traits were provided by the “Fazenda Vera Cruz”, farm located in Barra do Garças, Mato Grosso State and from the Nellore Brazil breeding program coordinated by Associação Nacional de Criadores e Pesquisadores (ANCP)
The results observed in this study demonstrated that birth weight showed higher discrimination power, and as the female’s age advances, the discrimination power of post-weaning weights was lower
Summary
The beef cattle economic profitability is directly related to reproductive efficiency and age at puberty, since reproductive traits determine the number of calves available for market (Baldi et al 2008). The zebu beef breeds are considered nonprecocious, since the age at puberty varied from 22 to 36 months, which reflects age at first calving (AFCa) ranging from 34 to 45 months (Dias et al 2004, Azevedo et al 2006) This pattern is attributed, mainly, to the use of body weight near the mating season as the main criterion for the reproduction of heifers, which a minimum of heifer weight of 70% of adult weight is adopted, and often results in a late exposure of heifers and late AFCa. This pattern is attributed, mainly, to the use of body weight near the mating season as the main criterion for the reproduction of heifers, which a minimum of heifer weight of 70% of adult weight is adopted, and often results in a late exposure of heifers and late AFCa This is one of the main reasons of the low economic result of beef cattle breeding systems in tropical regions. Lower selection pressure for reproductive efficiency related traits was observed in zebu cattle in relation to taurine cattle (Azevedo et al 2006)
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