PERFORMANCE, CARCASS, AND PALATABILITY TRAITS FOR CULL COWS FED HIGH-ENERGY CONCENTRATE DIETS FOR 0, 14, 28, 42, OR 56 DAYS

Cull cows, thin to moderate in initial condition scores, were randomly assigned within breed to slaughter groups and fed a high-concentrate diet for 0, 14, 28, 42 or 56 d (n = 40). Carcass data were collected, and one side of each carcass was fabricated into boneless subprimals, lean trimmings, fat, and bone. Live and carcass weights, ADG, and dres sing percentage increased through 28 d of feeding (P < .05), and lean firmness increased(P < .05) through 42 d of feeding. Adjusted prelimin ary yield grades and final yield grades increased (P < .05) with feedi ng, but not to levels requiring knife trimming of fat. Fat color becam e whiter (P < .05) but marbling was not affected (P > .05) by feeding. Weights of fat-free lean, fat, and bone and percentages of fat in sof t tissues of cow carcasses increased (P < .05) by 28 d on feed. Overal l steak tenderness was higher (P < .05) for cows fed 56 d than for cow s fed 0 or 14 d. Warner-Bratzler shear force was not affected by feedi ng. Amounts of soluble collagen increased (P < .05) in the longissimus muscle between 0 and 28 d on feed, and total collagen decreased (P < .05) in the biceps femoris muscle between 0 and 42 d on feed. Continen tal European cow carcasses yielded more fat-free lean and less fat (P < .05) and dairy cows generally provided the most tender product acros s all slaughter periods. In general, sensory tenderness and yields of cow carcass components increased without requiring excessive trimming of fat by feeding cull beef and dairy cows for periods up to 56 d.