Periódicos Brasileiros em Medicina Veterinária e Zootecnia

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Environmental and genetic effects of reactivity traits in Île-de-France x Texel crossbred lambs

Tamioso, Priscilla ReginaDias, Laila TalaricoTeixeira, Rodrigo de AlmeidaNascimento, Bárbara MazettiSilva, Gisele Ferreira daPortes, Juliana Varchaki

Background: Reactivity in livestock species has been assessed in relation to the behavioral reactions of animals, through restrained and non-restrained tests. Environmental and genetic parameters for reactivity traits have been reported for farm animals, as sheep, providing support for the possibility of direct selection. Despite evidences, there is little information on how genetic and environmental factors affect the expression of reactivity in sheep during and after weighing. Therefore, this study aimed to estimate the environmental and genetic effects of reactivity traits in Île-de-France x Texel crossbred lambs.Materials, Methods & Results: Reactivity traits from 188 Île-de-France x Texel cross lambs, aged between 28 and 110 days-old, were assessed in two situations: 1- During weighing: a. vocalization (VOC), b. movement (MOV), c. tension (TEN), d. exploratory behavior (EB) and e. ears posture (EP), and 2- After exiting the weighing crate, in a chute, through: a. gait speed (GS) and b. flight speed (FS) tests. For the study of environmental effects the model considered the fixed effects of month of assessment, sex and management group and as covariates, the linear effects of type of birth, age of dam and age of lamb. The (co)variance and genetic parameters were estimated using REML in univariate analysis and the direct additive genetic effect was considered in the model as a random effect. From all the environmental effects, month of assessment was statistically important over all the reactivity traits. Similarly, the effects of age of dam and age of lamb were significant for almost all variables.[...](AU)

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