Sire contemporary group interactions for birth weight and preweaning growth traits in the Asturiana de los Valles beef cattle breed

Although a number of recent studies have focused on the existence of a non-negligible sire contemporary group interaction effect (s) affecting the estimation of genetic parameters for maternally influenced traits in beef cattle, the assessment and interpretation of this effect using field data remains poorly understood. In this study 27,639 records of both birth weight (BW) and weaning weight (WW) from the Asturiana de los Valles breed were used to assess the consequences of the inclusion of an s effect on the estimation of genetic parameters for BW, WW and average daily gain (ADG) fitting univariate and bivariate models. Estimations of s for BW, WW and ADG were 0.040, 0.070 and 0.077 regardless of the fitted model. Inclusion of s in the estimation models induced a reduction of both the direct and the maternal heritability, varying between 8 and 28% with the trait and the estimation model employed. As expected, the correlations between both direct and maternal genetic effects for each trait were less negative when s was included in the estimation model. The estimated correlations between the s effect affecting BW, WW and ADG were 0.108, 0.038 and 0.616 for the pairs BW–WW, BW–ADG and WW–ADG, respectively. These results suggest that misidentification of individuals cannot be the sole cause of the effect of s and that this effect is of a different nature and origin for different traits (i.e. selective matings for low BW’s and unaccounted management practices for preweaning growth traits). Models including the s effect should be accepted as working models in beef improvement schemes. D 2005 Elsevier B.V. All rights reserved.