Factors affecting carcass traits of beef

Seven-hundred-thirty-six carcasses from Shorthorn, Angus, Hereford, and Charolais-cross (XB) steers were utilized in a three-year study of breed variation in beef carcass quality and yield traits. These steers were entries in the 1970, 1971, and 1972 Knoxville Finished Cattle Show.

Data collected relative to performance (carcass weight and carcass weight per day of age) indicated a significant (P < .01) advantage for crossbreds over the three British breeds. The carcass weight per day of age for crossbred carcasses was 1.31 pounds compared to hot carcass weights of 561.09 pounds for the British breeds.

A least squares (ANOV) indicated that breed means, with respect to hot carcass weight, were significantly different (P < .01) between (XB) and British breeds. No significant differences were indicated by a (OMR) test in mean hot carcass weights of the three British breeds; however, the (XB) steers produced carcasses heavier than the British breeds on an age-constant basis.

Angus carcasses had the highest mean carcass grade (Choice -) of the four breed groups. Shorthorn carcasses ranked next with a mean carcass grade of Good (+). A significant (P < .01) difference existed between these two breeds. The Hereford carcasses were not significantly different from Shorthorn carcasses; however, the (XB) carcasses had the lowest average carcass quality grade of the four breeds. No significant difference due to year existed in the mean carcass grades during the three-year study.

Age of steers had a significant (P < .01) positive effect on carcass quality grade and marbling score. Analysis of variance of carcass quality traits indicated a significant (P < .01) difference in breed effect on carcass quality grade.

Carcasses from the three British breeds averaged 0.45 inch and (XB) carcasses averaged 0.32 inch carcass fat thickness. This variation was significant at the (P < .01) level. A significant (P < .01) negative correlation (r = -0.87) existed between carcass fat thickness and percent retail cuts. Variation in overall carcass fat thickness due to year was not significant.

Carcasses from (XB) steers averaged 12.57 square inches (REA) and were more desirable (P < .05) than the British breed with respect to (REA). Angus carcasses averaged 11.27 square inches (REA) and were more desirable (P < .05) than (S) and (H) carcasses which were not different with respect to (REA). Year had a significant (P < C.05) influence on mean (REA).

Crossbred carcasses were estimated to yield a significantly (P < .05) higher percent retail cuts than (A), (H), or (S) carcasses. The three British breeds were not different with respect to predicted percent retail cuts. Angus carcasses were superior in retail cuts to carcasses from (S) and (H) steers, but this difference was not significant.

A regression of percent retail cuts on age-in-days resulted in a significant (P < .01) negative coefficient.