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Arquivo Brasileiro de Medicina Veterinária e Zootecnia

Print version ISSN 0102-0935On-line version ISSN 1678-4162


MARQUES, L.F.A. et al. Variance components and genetic parameters estimates for growth traits of Simmental cattle in Brazil. Arq. Bras. Med. Vet. Zootec. [online]. 1999, vol.51, n.4, pp.363-370. ISSN 1678-4162.

Birth, 100-day, weaning and yearling weights of 7587 Simmental cattle, and 25,812 pedigree data were used to estimate genetic parameters using different animal models. The simplest model (model l) included additive genetic and residual random effects. Models 2 and 3 were the same as model 1, but included, respectively, maternal permanent and maternal genetic effects. Model 4 did not include permanent effect. The most complete model (model 6) also included maternal additive and permanent effects, assuming covariance between them. Model 5 was the same as model 6, but did not included direct maternal covariance. Contemporary groups considered animals born in the same herd, year and season, from the same sex and raised under the same nutritional system. The models were compared using likelihood ratio tests. The (co)variance components and the genetic parameters decreased from the most simple (model 1) to the most complete model (model 6). One-hundred-day weight showed no (.00±.00) maternal genetic variance but moderate maternal environmental permanent effect (.17±.07). The maternal effects were important (P<.01) from birth to yearling. Maternal effects were important for weight traits of Simmental cattle and should be considered in genetic evaluations. However, comparing the values of maternal effects from models with and without permanent effects suggest confounding between these effects.

Keywords : Beef cattle; Simmental; animal model; growth traits; genetic parameters.

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