Resumen

DOMINGUEZ-VIVEROS, Joel et al. Adjustment of random regression models on genetic evaluations of Tropicarne cattle. Agrociencia [online]. 2011, vol.45, n.3, pp.325-337. ISSN 2521-9766.

The growth curve of cattle has a sigmoid shape that can be adjusted with random regression models. The objective of this study was to adjust a random regression model based on Legendre polynomials and to estimate components of variance and genetic parameters for data on growth of Tropicarne cattle. Information from 12 890 monthly weighings of 1787 calves, from birth to 24 months old, was analyzed. The pedigree included 2504 animals. Twenty-seven linear, quadratic and cubic models were compared for adjustment of the genetic (EGA) and animal permanent environmental (APA) effects, with three structures in residuals variances (homogeneous and heterogeneous of six and twelve classes). Once the model was selected with the animal effects, another nine models were analyzed to determine the possible addition of maternal genetic (EGM) and permanent environmental (APM) effects. The analyses were performed with the DFREML software. Models were compared based on the likelihood ratio test, Akaike's information criterion, and the Bayesian information criterion. The model with the best fit included the quadratic order EGA and the effects of APA, EGM and APM of cubic order, with heterogeneous residual variance in twelve classes. The phenotypic variances, EGA and EGM, showed a positive trend on age; however, the residual variance showed quadratic behavior in the first eight months of growth after which it remained constant. Average direct heritability was 0.079 with values of 0.006 to 0.06 up to seven months of age; as of eight months it was constant, around 0.11. Average maternal heritability was 0.084, with values of 0.02 to 0.06 up to seven months and 0.07 to 0.16 as of eight months of age. The random regression model was well fitted as of nine months of age, but it underestimated the genetic parameters for younger ages.

Palabras llave : cattle; genetic improvement; genetic parameters.

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