Implicações da interação genótipo x ambiente na seleção de bovinos da raça Nelore

• Ano de defesa: 2016
• Autor(a) principal: Fernanda Santos Silva Raidan
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Crescimento; Sistema de produção; Intensidade de seleção; Reprodução; Herdabilidade; Nelore (Zebu) Aspectos geneticos; Genética animal; Nelore (Zebu) Aspectos ambientais
• Link de acesso: http://hdl.handle.net/1843/BUOS-ARBHTX

The selection of bulls may be done in favorable, challenging or similar environments to raised their progeny, because the environment to raised the progenie's of bulls is not defined in advance their production. The identification of the environment that results in the greater, direct and indirect, response to selection, would facilitate the process of selection and evaluation of the performance for selection candidates. Thus, this study aimed to compare the efficiency of pasture or feedlot production systems for performance evaluation and selection of sires in beef cattle. Genetic parameters for final weight (FW), average daily weight gain (ADG) and scrotal circumference (SC) of Nellore young bulls raised in individual performance tests on pasture or in feedlot were obtained. The additive genetic and residual variances and heritability vary according to environment and the greater values were observed for animals raised in feedlot systems. The genetic correlations between the same trait measured on pasture or in feedlot were lower than one. Traits of lower heritability are more sensitive to genotype x environment interaction. Variations in the selection intensity practiced on pasture or in feedlot contribute for reducing differences in, direct and indirect, responses to selection obtained in these two environments. Additionally, we presented correlated responses for growth and reproductive traits in commercial animals when selection was applied in performance-tested young bulls, both on pasture and feedlots. Heritabilities for growth and SC are greater in performance-tested young bulls than in commercial animals. The genetic correlations between traits in performance-tested and commercial herds were positive, except for pairs that included age at first calving (AFC). The AFC was genetically related to ADG and SC in performance-tested young bulls on pasture, however it was not related to these traits in performance-tested young bulls in feedlots. Thus, the individual performance test on pasture can be used for performance evaluation and selection of sires regardless of raised environment of the progenies.