Resumo

CASTRO, J.; ROQUETE, C.  e  BARATA, G.. Evaluation of selection response in a population of mertolengo beef cattle. Rev. de Ciências Agrárias [online]. 2007, vol.30, n.1, pp.223-234. ISSN 0871-018X.

The "Mertolengo" is a Portuguese native beef breed witch inhabits in the Alentejo country (south of Portugal). It is very well adapted to perform in range production systems. A herd of Mertolengo breed were utilized for the evaluation of response to selection, over forteen years. Field data were recorded and the weights were adjusted for 3 and 6 months of age. For those traits, realized heritabilities were estimated, combining the two sexes and utilizing the total response to selection and the weighted cumulative selection differentials. The values reached were, respectively, 0,28 and 0,29 for 3 months and 6 months age weight. The evaluation of selection response, on the female side, fallowed the gene flow method referred by Elsen & Mocquot (1974), taking in account the age structure of the female population. Through this method it was possible to evaluate the changes year by year. The female contribution to the genetic progress was very low, and frequently negative, when compared with bulls. The amount of response achieved was entirely due to the bulls.

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