Data collected on birth and weaning weight traits of beef cattle calves over the period of 1968 to 1992 with varying levels of Angus and Charolais genes, ranging from 0% to 75%, were analysed to determine possible optimum breeding levels for birth weight (BW), weaning weight (WW) and pre-weaning average daily gain (ADG), fitting a unitrait animal model. The estimated heritabilities were used to predict direct (DBV) and maternal breeding values (MBV) for each animal. Best Linear Unbiased Estimates (BLUEs), DBVs and MBVs per genetic group estimated were regressed on proportions of Charolais and Angus breeding. BLUEs of the traits increased with increasing proportion of Charolais, while they decreased with increasing Angus breeding levels. In general, MBVs increased with increasing the proportions of both breeds. DBVs of the Charolais increased and reached a maximum at 35, 38, and 45% proportions of Charolais for BW, WW and ADG, respectively. Except for BW, DBVs of WW and ADG decreased as the genetic contribution of the Angus increased. No optimal Angus proportion was found in this herd within the specific environmental condition. It is suggested that increasing the proportion of the Charolais to intermediate levels would tend to improve the performances of pre-weaning traits.
"Experientia docet" - Experience is the best teacher