Nutritional effects on beef collagen characteristics and palatability

Abstract

To determine effects of different nutritional regimens on beef palatability and collagen characteristics, we randomly assigned 18 Hereford steers of similar age and nutritional background to three treatment groups: group 1 was slaughtered directly off pasture at about 19 to 20 months of age; group 2, composed of animals the same age as those in group 1, was slaughtered after being fed a high energy diet for 120 days, and group 3, 23 to 24 months of age, was slaughtered after 126 days on a high energy diet. Feeding the high energy diet increased USDA quality and yield grades. Longissimus (LD) steaks from the three groups did not differ in total collagen content, sarcomere length, Warner-Bratzler shear force, cooking loss or sensory panel ratings for tenderness, juiciness and flavor intensity. However, LD samples from group 3 animals had a higher (P<.05) percentage of salt plus acid soluble collagen and less organoleptically detectable connective tissue than LD samples from group 1. LD samples from group 2 animals had a higher (P<.05) percentage of salt soluble collagen than those from group 1. Biceps fernoris (BF) steaks from group 1 steers were juicier than those from groups 2 and 3. Feeding regimen did not consistently affect BF collagen solubility, taste panel tenderness or shear force. Beef from grass-finished cattle received acceptable taste panel scores. The effects of the high energy diet on plasma nonprotein hydroxyproline content and live animal weight were monitored in group 3. Plasma nonprotein hydroxyproline content (an indicator of collagen degradation) was highest at approximately 42 days on feed and corresponded well with weight gain. These results suggest that collagen turnover is accelerated during the rapid growth phase of cattle fed a high energy diet.