Suckler cow efficiency - breed by environment interactions in commercial herds under various natural production conditions

The significance of breed by environment interaction on suckler cow efficiency traits was investigated, using production data from the Norwegian Beef Cattle Recording System and data collected (feed regimes, etc.) from 27 commercial suckler cow herds. Two statistical approaches were used; mean breed performance in extensive/intensive environments (mixed models), or as within breed regressions of cow performance on modelled cow energy intake. Aberdeen Angus produced higher weaning weight than Hereford below 12,000 MJ NE (241 kg) and Charolais below 13,000 MJ NE (244 kg) cow energy intake in the suckler period, after which the breeds re-ranked. The corresponding re-rank between Hereford and Charolais was at 14,500 MJ NE (263 kg) cow energy intake. Overall, breed by environment interactions were observed for calving interval, number/kg calves weaned/mated cow/year and energy efficiency, which emphasise that choice of cow breed should be dependent on the natural production resources available.