Palatability and Muscle Properties of Beef as Influenced by Preslaughter Growth Rate

Abstract

Thirty-six Hereford-Angus yearling steers, average weight 247 kg, were assigned to one of three feeding regimens for 120 d. Treatment 1 (T-1) steers were fed ad libitum to obtain maximal weight gain; average daily gain (ADG) was 1.42 kg. Treatment 2 (T-2) steers were restricted to an ADG of .77 kg. Treatment 3 (T-3) steers were restriced to an ADG of .34 kg. Postslaughter chilling was slowed in the left sides of carcasses from T-2 and T-3 cattle so that the rate of temperature decline in the longissimus (LD) muscle matched that of the fatter, heavier carcasses from T-1. A trained sensory panel rated steaks from the LD and semimembranosus (SM) muscles of T-1 steers more tender (P<.05) than those from the left side of T-2 and T-3. The SM from T-3 was less (P<.05) tender than that from T-2. Significant tenderness differences among treatments were not detected with Warner-Bratzler shear, although the ranking among treatments was the same as obtained with sensory analysis. Lower tenderness scores of T-3 SM were associated with higher (P<.05) intra-muscular collagen thermal-shrinkage temperature, lower (P<.05) percentage soluble collagen and slightly higher (P>.05) total collagen. Plasma nonprotein hydroxyproline concentrations were lower in T-3 steers throughout the feeding period. Lower tenderness in the LD of the T-3 group may have reflected the shorter sarcomeres in this muscle than in that from either T-1 or T-2, even though carcasses were chilled at similar rates. Myofibril fragmentation did not differ among treatments. Results show that growth rate before slaughter affects beef tenderness, a relationship that may be mediated partly through the turnover and(or) maturation rate of intramuscular collagen and also through effects of growth rate on sarcomere length. Copyright © 1985. American Society of Animal Science . Copyright 1985 by American Society of Animal Science