CARCASS CHARACTERISTICS AND BEEF PALATABILITY AS INFLUENCED BY FEEDING RICE STRAW AND ALFALFA

Ninety feeder steers, predominantly Herefords weighing 280 kg, were assigned at random to each of nine diets: basal (high concentrate); 25 or 50% of untreated rice straw (25- or 50 URS) or ammoniated rice straw (25- or 50 ARS); a 50:50 mixture of URS - alfalfa or ARS - alfalfa replacing a proportion of the basal at 25 and 50%. Animals were slaughtered after 154 or 161 days of feeding. The cattle fed 50% URS had the lowest (P<.05) carcass weight, dressing & external fat thickness, kidney, pelvic and heart fat, rib eye area, marbling score, quality and yield grades, followed by cattle fed 50% ARS, 50% rice straw/alfalfa, and 25% rice straw alone or 25% rice straw/alfalfa mixture. Ammoniation of rice straw improved all measured traits. A 25% substitution of basal diet with untreated or ammoniated rice straw and a 50% substitution with rice straw/alfalfa mixture did not significantly affect carcass traits compared to the basal group. Only 50% ARS and 50% URS cattle showed differences in body composition (P<.05) with lower fat and higher water and protein contents. No significant differences were found in shear value, panel tenderness, connective tissue, juiciness, flavor and overall palatability of meat from steers fed the basal, ARS or URS diets.