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Revista Brasileira de Zootecnia

Print version ISSN 1516-3598On-line version ISSN 1806-9290


TORAL, Fábio Luiz Buranelo; ALENCAR, Maurício Mello de  and  FREITAS, Alfredo Ribeiro de. Fixed effects arrays and residual covariance structures to analyze sequential weights of Canchim beef cattle. R. Bras. Zootec. [online]. 2006, vol.35, n.5, pp.1951-1958. ISSN 1516-3598.

The aim of this work was to evaluate arrays of fixed effects and residual covariance structures that best fit the herd and the animal variability to weights at birth, weaning, twelve and eighteen months of 3,690 Canchim animals. Different arrays of fixed effects (contemporary groups and, or the main effects of year, month or season of birth and sex) and different residual covariance structures (considering or not change of variance and of correlation between weights at different ages) were studied. The results indicated that the most adequate array of fixed effects to fit herd variability was the contemporary group of year, month and sex. The best residual covariance structures were the First-Order Factor Analytic and the Unstructured, which consider increase of residual variance as age increases and different correlation between pair of weights at different ages.

Keywords : contemporary groups; longitudinal data; main effects; residual correlation.

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