Quantitative genetic study at production traits of Nellore cattle raised in Northern, Brazil

Ferreira J.L., Lopes F.B., Marques E.G., Silva M.C., Assis A.S., Pereira L.S. & Nepomuceno L.L. [Quantitative genetic study at production traits of Nellore cattle raised in Northern, Brazil.] Estudo genético quantitativo em características produtivas de bovinos da raça Nelore criados na Região Norte do Brasil. Revista Brasileira de Medicina Veterinária, 36(1):11-17, 2014. Programa de Pós-Graduação em Ciência Animal Tropical, Universidade Federal do Tocantins, BR 153 Km 112, Caixa Postal 132, Zona Rural, Araguaína, TO 77804-970, Brasil. E-mail: jlferreira@uft.edu.br Effective research related to quantitative genetic analyzes of growth traits in Northern Brazil, are incipient. Thus, this study was carried out to analyze data of calculated weight at 205 (W205), 365 (W365) and 550 (W550) days old and days to gain 160 kg (D160) pre-weaning and days to gain 240 kg (D240) post- -weaning of Nellore cattle raised on pasture from Humid Tropics. It was used animal mixed model. As fixed effects were included the contemporary group and covariate age of cow and as random effects were included the additive direct genetic and residual. It was used restricted maximum likelihood method by the MTDFREML. Estimates of heritability were 0.27 (W205), 0.54 (W365), 0.39 (W550), 0.23 (D160) and 0.24 (D240). Estimates of genetic correlations between P365 and P450, P365 and P550 and between P450 and P550 were 0.98, 0.94 and 0.98, respectively. Selection responses to for W365, W450 and W550 were favorable indicating that the selection criteria adopted in these farms are favoring genetically these traits. Estimates of heritability showed high magnitude, as well as genetic correlations between traits, indicating that both indirect and direct selection would cause changes in the average population for these traits.