EFFECTS OF SLAUGHTER AGE ON MEAT TENDERNESS AND USDA CARCASS MATURITYSCORES OF BEEF FEMALES

Two experiments were conducted to determine the effect of carcass matu rity on meat palatability using concentrate-fed cattle of known histor y and to determine the relationship of chronological age to carcass ma turity scores. Yearling heifers (n = 28) and 2-yr-old cows (n = 25) of similar breed groups were fed a high-energy-density diet for 90 d bef ore slaughter. Longissimus muscle Instron peak load (Warner-Bratzler s hear force) did not differ between age groups; but, fail elongation wa s higher for the 2-yr-old cows (P < .05). Overall tenderness ratings w ere lower for the 2-yr-old cows; however, the magnitude of the tendern ess difference between age groups was small (.4 units on an 8-point sc ale). There was 10-fold more variation in tenderness within each age g roup than there was between age groups. Carcass maturity scores and ch ronological age were compared for heifers and cows (n = 249) ranging i n age from 1.7 to 13.9 yr. Carcass maturity scores increased with incr easing chronological age at a much faster rate than indicated by USDA. The following chronological age groups most accurately reflected the chronological age associated with each USDA carcass maturity class: A, 9 to 24 mo; B, 24 to 36 mo; C, 36 to 48 mo; D, 48 to 60 mo; E, > 60 m o. These results indicate that efforts to control variation in tendern ess would be more effective if they targeted factors that have a great er effect on meat tenderness than does maturity class. Moreover, our r esults indicate that cows may grade lower at a given age than what USD A standards imply.