CARCASS AND MEAT QUALITY CHARACTERISTICS OF PASTURE-FED UNBRED AND ONCE-BRED HEREFORD X FRIESIAN HEIFERS

Carcass and meat quality traits of Hereford x Friesian once-bred (''ca lved'') heifers (n = 15) were compared with those of bred but not preg nant (''empty'') heifers (n = 10) and ''unbred'' heifers (n = 10). Unb red and empty heifers had similar carcass weights (mean = 242 kg), but the mean carcass weight of the calved heifers was 31 kg less (P < 0.0 01) even though they were 6 months older. Weight-adjusted dressing-out percentages were lower (P < 0.05) in calved heifers than in unbred he ifers, with values for the empty group being intermediate. Calved heif ers had longer carcasses and femur bones than unbred (P < 0.05) and em pty (P < 0.001) heifers at the same carcass weight. Hind-quarter cut y ields were highest for the calved group. Measures of fatness adjusted for carcass weight were generally lower for the calved group, but diff erences were seldom significant. Meat quality was assessed on samples of Longissimus dorsi collected before chilling at c. 90 min post-morte m and kept above 12 degrees C for 24 h. Beef of calved heifers was sig nificantly brighter (i.e. higher reflectance values, P < 0.05) than me at from unbred heifers, with the empty group having intermediate value s. Overall, Warner-Bratzler shear force parameters as measures of meat tenderness were similar for meat from unbred, empty, and calved heife rs. It is concluded that, relative to unbred heifers, the quality of m eat and carcasses of heifers that have raised one calf on pasture to c . 5 months of age will be similar, although at the same carcass weight , skeletal dimensions will be greater and dressing-out percentages sli ghtly lower. Thus the attractive features of once-bred heifer producti on from the point of view of efficiency are unlikely to be offset by c hanges in carcass or meat quality. In a second experiment, meat qualit y characteristics were compared for samples of Longissimus dorsi from the carcasses of 28 once-bred heifers either before (as for Experiment 1) or after chilling. Some significant differences existed between th e pre- and post-chill samples but the correlations obtained were gener ally moderate to high indicating that taking samples before chilling, in addition to avoiding variation in cold-shortening, also gave qualit y results similar to those obtained under commercial conditions.