title: Effects of slaughter age on meat tenderness and USDA carcass maturity scores of beef females.
abstract: Two experiments were conducted to determine the effect of carcass maturity on meat palatability using concentrate-fed cattle of known history and to determine the relationship of chronological age to carcass maturity 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 before slaughter. Longissimus muscle Instron peak load (Warner-Bratzler shear force) did not differ between age groups; but, fail elongation was higher for the 2-yr-old cows (P < .05). Overall tenderness ratings were lower for the 2-yr-old cows; however, the magnitude of the tenderness difference between age groups was small (.4 units on an 8-point scale). There was 10-fold more variation in tenderness within each age group than there was between age groups. Carcass maturity scores and chronological age were compared for heifers and cows (n = 249) ranging in age from 1.7 to 13.9 yr. Carcass maturity scores increased with increasing 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 mo. These results indicate that efforts to control variation in tenderness would be more effective if they targeted factors that have a greater effect on meat tenderness than does maturity class. Moreover, our results indicate that cows may grade lower at a given age than what USDA standards imply.
authors.affiliation: Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, NE 68933-0166, USA.
authors.forename: S D
authors.initials: SD
authors.lastname: Shackelford
authors.forename: M
authors.initials: M
authors.lastname: Koohmaraie
authors.forename: T L
authors.initials: TL
authors.lastname: Wheeler
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001823:Body Composition / Q000502:physiology*; D002417:Cattle / Q000502:physiology*; D005260:Female; D005524:Food Technology / Q000379:methods / Q000592:standards; D008460:Meat / Q000592:standards*; D018482:Muscle, Skeletal / Q000502:physiology; D014481:United States; D016885:United States Department of Agriculture