Genetic variability underlying maternal traits of Asturiana de la Montaña beef cattle

Genetic variability parameters of traits related to maternal ability (age at first calving–CA1, first calving inter-val–CI1, and weaning weight–WW) were estimated in an autochthonous beef cattle breed (Asturiana de la Montaña) reared under harsh conditions. The data set comprised 50,749 births on 378 farms from 1994 to 2008. Heritability for CA1 was moderately high (0.22); heritability for CI1 was 0.10. Genetic correlation between these traits was 0.54, and thus favourable to simultaneously selection. Results for WW gave a direct heritability of 0.20 and a ma-ternal heritability of 0.10; the genetic correlation between additive direct effects and additive maternal effects was –0.60 and thus antagonistic, a situation frequently found in similar populations. The change of additive direct values (BVa) for the lapse considered was almost null until 1997, and increased regularly since that year at 0.092 kg yr–1. It should be noted that, at the same time, additive maternal effects (BVm) showed a significant negative tendency of –0.089 kg yr–1. In order to conveniently combine the knowledge on both genetic effects, taking into account the adverse genetic correlation between them, we propose that selection should be based on a global genetic merit index (BVtm) defined as 1⁄2 BVa + BVm. Correlations between BVa and BVtm, and between BVm and BVtm were 0.22 and 0.56, respectively. Additional key words: additive effects; autochthonous breed; maternal effects; merit index