Collagen Stability, Testosterone Secretion and Meat Tenderness in Growing Bulls and Steers

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Abstract
Interrelationships among concentration and maturation of intramuscular collagen, serum concentration of hydroxyproline and testosterone and meat tenderness were determined in growing bulls and steers. Sixty-four Charolais × Angus bulls were assigned to sex treatment groups (intact or castrate) and slaughter groups (9, 12, 15 or 18 mo of age). Animals were bled at 30-min intervals via intrajugular catheters between 0600 and 1400 beginning 48 h before slaughter. Serum concentrations of testosterone were determined in each sample from bulls and from four samples from steers; serum hydroxyproline was determined in the last sample from both sexes. Testosterone mean values for the collection period were calculated. Samples of the longissimus, semitendinosus and infraspinatus muscles secured within 45 min postmortem were analyzed for intramuscular collagen concentration, percent soluble collagen and collagen thermal shrinkage temperature. Tenderness of loin steaks was determined by Warner-Bratzler shear test. Serum concentrations of hydroxyproline and testosterone were higher (P<.01) in bulls than steers. Age effects were noted for both hydroxyproline (P<.01) and testosterone (P<.06). Total intramuscular collagen was greater (P<.01) in bulls than steers and was different (P<.01) among muscles, but the muscle differences were not uniform over all ages (P<.05). Percent soluble collagen declined (P<.01) with age and was different (P<.01) among muscles. Interaction of age and muscle (P<.01) and age and sex (P<.05) also were noted for percent soluble collagen. Collagen shrinkage temperature increased (P<.01) with age. Steak tenderness was similar between sexes and over all ages but was more variable in bulls than steers. These data indicate that bulls have greater quantities of intramuscular collagen that matures more rapidly than that of steers. Copyright © 1987. American Society of Animal Science . Copyright 1987 by American Society of Animal Science.