Abstract
Genetic breeding programs of beef cattle in Brazil are including new features, mainly related to reproductive efficiency.Thus, it is necessary to study the effectiveness of selection and quantify genetic gain for these traits in herds. This study estimated genetic and phenotypic parameters and genetic trends for reproductive traits used in breeding programs for Nelore beef cattle. The traits studied were the scrotal circumference (SC) at 365 and 450 days of age (SC365 and SC450), age at first calving (AFC) and gestation length, as a cow trait (GLcow) and a calf trait (GLcalf). The (co)variance components were obtained with the Restricted Maximum Likelihood Methodology in a single and double-trait analysis of the animal model. For scrotal circumference (SC365 and SC450), positive and favorable genetic gains were observed. For AFC, GLcow and GLcalf, the trends were favorable for selection, but without significant genetic gain. Selection for large SC may reduce AFC and improve female reproductive efficiency. The selection for reproductive traits (SC365, SC450, AFC and GL) may improve reproductive and productive efficiency of Nelore cattle, if used as a selection criterion.
Highlights
New market concepts aim toprovide agricultural and livestock products in sustainable production systems
at first calving (AFC) was measured in months, obtained from the difference between the birth date and date of first calving; gestation length (GL) was measured in days, obtained from the difference between insemination date and calving date, which was obtained for cow trait (GLcow) and calf trait (GLcalf)
AFC genetic variability can be obtained from direct selection,the methods cited above should be improved in order to explore the trait variability, which could bring direct economic efficiency, profitability and competitiveness of Brazilian cattle (Boligon; Rorato; Albuquerque, 2008)
Summary
New market concepts aim toprovide agricultural and livestock products in sustainable production systems. Animal genetic breeding is one of the multidisciplinary tools for this new beef cattle system to meet basic requirements of the sustainable production process. Genetic breeding allowstoreduce production cycle, maximizing productive and reproductive potential of the herd, that is, animals with precocious sexual development, growth and carcass finishing. This can increase improve quality and increase production of Brazilian meat products. Traits related to reproduction have a great impact on profitability in animal production systems. Selection criteria connected to with sexual precocity and reproductive efficiency have been used widely in genetic breeding programs in Brazil (Lôbo et al, 2010)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
