Evaluation of British Friesian, Canadian Holstein and beef breed × British Friesian steers slaughtered over a commercial range of fatness from 16-month and 24-month beef production systems 2. Carcass characteristics, and rate and efficiency of lean gain

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Abstract
Carcass characteristics, and the rate and efficiency of lean gain of purebred British Friesian and Canadian Holstein steers and of crossbred steers out of British Friesian dams by Charolais, Hereford, Limousin, Lincoln Red, Simmental, South Devon and Sussex sires were examined in two beef production systems. One was similar to the commercial 18-month grass/cereal system (16-month) and the other to a commercial 2-year system (24-month). The cattle were serially slaughtered at three pre-determined fatness levels, estimated by the Scanogram ultrasonic machine. The trial extended over 4 years and involved a total of 650 cattle, 398 of which had their left sides separated into tissues. Breeds were compared at equal carcass subcutaneous fat proportion determined by visual carcass assessment (SFe). Data for the two production systems were analysed separately.Sire breed differences were not detected in the regression on SFe for most characteristics (P > 0·05). Sire breeds differed in killing out and visual conformation score in both production systems (P < 0·001): Charolais and Limousin crosses had the highest values and purebred Canadian Holsteins the lowest. The overall range between sire breeds was 30 g carcass weight per kg live weight and five points on a 15-point conformation scale.Breeds with the higher conformation scores generally had higher carcass lean proportions and higher lean: bone ratios. Canadian Holsteins had a 20 g/kg lower carcass lean proportion than the British Friesians (P < 0·05).Breed crosses with larger adult body size tended to have higher lean tissue growth rates: the difference between mean values for Charolais crosses and Hereford crosses was 49 g/day (16-month) and 38 g/day (24-month). The lean tissue growth rates of the British Friesians and especially the Canadian Holsteins were low in relation to their adult body size.Limousin and Charolais crosses had the highest efficiency of lean gain (g lean per kg digestible organic matter intake). These and the other crosses were significantly more efficient than the purebred Canadian Holsteins (P < 0·05). The overall range between breeds was 20 g/kg.