Resumen

RIOS UTRERA, Ángel; MARTINEZ VELAZQUEZ, Guillermo; VEGA MURILLO, Vicente Eliezer  y  MONTANO BERMUDEZ, Moisés. Genetic effects for growth traits of Mexican Charolais and Charbray cattle estimated with alternative models. Rev. mex. de cienc. pecuarias [online]. 2012, vol.3, n.3, pp.275-290. ISSN 2448-6698.

Data recorded from 1 997 to 2009 by the Charolais-Charbray Herd Book of Mexico were analyzed with six different animal models to estimate genetic parameters for birth weight (n=1 05,599), weaning weight adjusted to 205 d (n=89,111 ) and yearling weight adjusted to 365 days (n=55,284). Model 1 included direct additive genetic effects of the animal. Model 2 allowed for a common environmental effect due to the dam, fitting it as an additional random effect. Model 3 included the animal's direct genetic effect, and the dam's maternal genetic effect, assuming a covariance equal to zero between them. Model 4 was the same as Model 3 but it also allowed for a common environmental effect due to the dam. Model 5 is identical to Model 3, but included a covariance between direct and maternal genetic effects. Model 6 was fitted for all three random effects plus the covariance between direct and maternal genetic effects. Compared with any of the other models, the most complete model (Model 6) substantially reduced the -2log L (P<0.05), providing the best fit for the three growth traits. Comparison between Model 1 and Model 6 across traits showed that Model 1 yielded smaller estimates of direct genetic variance, in contrast with results from previous studies. However, estimates of the residual variance for Model 1 were significantly greater than estimates for Model 6.

Palabras llave : Genetic parameters; Growth traits; Beef cattle.

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