Characterization of differences in adipose and muscle tissues from double-muscled and normal cattle fed high or low energy rations

Abstract

Differences in adipose and skeletal muscle tissues between double-muscled (DM) cattle and normal cattle fed high energy or low energy rations were analyzed; 4 DM and 2 normal cattle were fed a high energy ration, while 3 DM and 3 normal cattle were fed a low energy ration. Biopsies were performed at 9, 12, 14, 18 and 23 months of age, and all animals were slaughtered at 27 months of age. Longissimus muscle, brisket fat and blood were obtained at all sampling times with the exception of the 9 month time at which time only muscle samples were removed. The brisket fats were analyzed for size and number of adipocytes. Serum lipid content was determined for the blood samples. Fiber type and size and number of muscle fibers were obtained. The longissimus muscle and the brisket fat taken at slaughter time were also analyzed for nucleic acid concentrations and NADPH-producing enzyme activities, respectively. Muscle samples removed at 48 hr postmortem were evaluated for palatability and the intramuscular collagen content was assayed. The DM cattle were lighter in live weight and warm carcass weight and had smaller ribeye areas than normal cattle. Moreover, the DM cattle had significantly higher dressing percentages and significantly lower amounts of subcutaneous, internal and intramuscular fats than normal cattle..