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Genetic antagonism between growth and maternal ability in nelore cattle

J.P. Eler^I; J.B.S. Ferran^II; R.B. Lobo^II; L.A. Josakian^III

^IDepartamento de Zootecnia, Faculdade de Zootecnia e Engenharia de Alimentos da Universidade de São Paulo, Caixa Postal 23, 13630-000 Pirassununga, SP, Brasil. Send correspondence to J.P.E.
^IIDepartamento de Genética, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, 14049-900 Ribeirão Preto, SP, Brasil
^IIIAssociação Brasileira de Criadores de Zebu (ABCZ), Liberaba, MG, Brasil

ABSTRACT

This study evaluated direct and maternal effects on 205 and 365 day weights (W205 and W365) of 7415 Nelore calves, sired by 59 bull: and raised on pasture in the state of São Paulo, Brazil. Thirteen variance and covariance components for several different sets of related animal: were estimated by least squares procedure and equated to their expected causal components. The system of equations gave estimates of heritability for direct effects (h_o²) and for maternal effects (h_m²). Estimates of h_o² were 0.26 for W205 and 0.18 for W365. The estimates of h_m² were 0.28 foi W205 and 0.18 for W365. The estimates of genetic correlations between the direct and maternal effects (r_Ao_Am) were -0.91 for both traits, suggesting a severe antagonism between the effects of genes for growth and genes for maternal ability. Estimates of total heritability (h_T²) were only 10% of those obtained by the usual paternal half-sib correlation. These results suggest that analyses that do not consider maternal effects in the Nelore breed overestimate genetic progress and long term response may be less than has been predicted.

Keywords: genetic antagonism; growth ability; maternal ability; nelore cattle.

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