Resumen

TORRES-VAZQUEZ, José Antonio et al. Genetic and phenotypic parameters for yearling weight, scrotal circumference and frame score in Simmental and Simbrah beef cattle from Mexico. Rev. mex. de cienc. pecuarias [online]. 2012, vol.3, n.3, pp.291-298. ISSN 2448-6698.

The objective of the present study was to estimate (co)variance components, heritabilities and genetic and phenotypic correlations for yearling weight (YW), scrotal circumference (SC) and frame score (FS) of Simmental and Simbrah young bulls from Mexico. All traits were adjusted to 365 d according to the Beef Improvement Federation (BIF). Final data file included 1 ,949 Simmental and 1,259 Simbrah records. A three-trait animal model was used to estimate (co)variance components and genetic parameters. For each trait, the model included fixed effects of herd-year-season, and the age of dam, gene proportion of Simmental breed, heterozygosity and recombination losses effects as covariates; animal and residual were included as random effects. Additive variances were 376.3±130.9 kg², 2.89±0.69 cm² and 0.37±0.08 units²; and heritabilities were 0.33±0.11, 0.35±0.08 y 0.42±0.08, for YW, SC and FS, respectively. Genetic correlations were 0.36±0.1 9, 0.47±0.1 7 and 0.59±0.12, for YW-SC, YW-FS and SC-FS, respectively. Heritability estimates show that a favorable response would exist to selection for the studied traits. Genetic correlations indicate that no genetic antagonisms exist, suggesting that would be a positive correlated response to selection of any trait. It would be necessary the use of selection indices in order to avoid greater FS as correlated response due to direct selection of YW and SC.

Palabras llave : Beef cattle; Frame score; Scrotal circumference; Genetic correlations; Heritability.

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