EFFECTS OF DIET AND SLAUGHTER END-POINT ON CARCASS COMPOSITION AND BEEF QUALITY IN CHAROLAIS CROSS STEERS

One hundred and eight Charolais cross steers were used to compare fora ge versus grain feeding as affected by slaughter endpoint on carcass c omposition and palatability attributes of beef. Diets included a 97% a lfalfa silage ration or 68% high moisture corn, 25% alfalfa silage rat ion from start of test to finish or a ration of 97% alfalfa silage fro m start of test to day 42 of the trial followed by the 68% high moistu re corn ration until slaughter. Cattle were slaughtered at either 4, 7 , or 10 mm ultrasound backfat. Grain feeding increased (P = 0.01) aver age daily gain and decreased (P = 0.01) days to finish, while carcass weight and grade fat were similar (P > 0.10) between diets. Palatabili ty attributes were generally unaffected by diet with the exception of slightly less (P = 0.09) beef flavour and more (P = 0.01) off flavour in forage-fed beef versus grain-fed beef. Higher (P = 0.01) concentrat ions of linolenic acid and lower (P = 0.09) concentrations of oleic ac id in forage-fed beef may be partially responsible for diet difference s in flavour. As slaughter endpoint increased from 4 to 7 mm backfat, average daily gain, days to finish, and carcass weight increased (P = 0.01). Palatability attributes assessing juiciness and flavour did not differ (P > 0.10) between slaughter endpoints. Beef from cattle slaug htered at 10 mm backfat was rated higher (P < 0.05) for softness, tend erness, acid chewiness than beef from cattle slaughtered at 4 and 7 mm finish. Slaughter endpoint effects on ''tenderness'' attributes may p artially explain why less tender beef is entering the marketplace.