Animal Science Department


Date of this Version



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Animal Science, Under the Supervision of Professor Chris R. Calkins. Lincoln, Nebraska: May, 2013

Copyright (c) 2013 Michelle E. Semler


The objectives of this study was to determine tenderness, nutrient, and musculature differences of loins from cattle with variation of myostatin gene. Steers (n = 21, 22, and 16) and heifers (n = 19, 20, and 20) were genotyped as homozygous (MM; active myostatin gene), heterozygous (Mm; partially recessive myostatin) or homozygous (mm; recessive inactive myostatin), respectively. At 3 d post mortem Longissimus dorsi (LD) and Semitendinosus (ST) were collected. Loins were cut into 2.5 cm thick steaks evaluated for: total number steaks, total number vein steaks, total number non-vein steaks, and individual steak weight. Nutrient analysis steaks were cut 1.3 cm thick and trimmed to 0.3 mm of fat. Warner-Bratzler shear force (WBS) was conducted on steaks aged for 14 d. Steaks from ST of MM steers had greater (P < 0.001) WBS values (3.6 vs. 3.1 kg) compared to mm. No differences in WBS values for the ST of heifers and LD of steers and heifers. Fat content from mm steaks decreased (P < 0.001) while moisture (P < 0.001) and protein increased (P < 0.001) compared to MM and Mm. Calories decreased with increasing copies of recessive gene (P < 0.001). Steaks from mm had greater concentrations of cholesterol (P < 0.001), decreased levels of saturated fatty acids (P P < 0.001), polyunsaturated fatty acids (P < 0.001) and trans fatty acids (P < 0.001) than MM. Fat thickness decreased (P < 0.001) for heterozygous and homozygous recessive cattle compared to homozygous dominant cattle. Weight and percentage of veins steaks did not differ for steers. Loins from Mm heifers had a decreased percentage of vein steaks (P = 0.01) compared to MM and mm steaks from heifers. In conclusion, steaks from mm cattle had decreased fat content, greater cholesterol concentrations, and greater protein concentrations compared to MM. Loins of steers exhibited no difference in proportion of weight and percentage of vein steaks.