Incidence of Marbling of Bovine and Porcine Longissimus

Marbling content of the longissimus (12th costae) was subjectively appraised for 2,436 beef carcasses originating from steers of several breed groups (Angus 1,219, Hereford 563, Shorthorn 407, Red Poll 37, other 210) exhibited at recent International Quality Beef Programs (1956 to 1965). Marbling appraisals were also made for 805 pork carcasses originating from barrows of nine breeds (Hampshire 324, Duroc 116, Poland China 106, Yorkshire 82, Berkshire 64, Chester White 54, Spotted Swine 37, Landrace 17, Tamworth 5) exhibited in carcass merit programs conducted in Wisconsin, Indiana and Illinois (1959 to 1966). Marbling variability was subjected to least squares analysis, and within breed and year correlation coefficients were calculated for comparisons between marbling score and several objective carcass traits. Results indicated that there was a significant breed difference in marbling content. In breef, Angus contained one-half score more marbling than Shorthorn, one score more than Herefords and about two scores more than Red Polls and other breeds; however longissimus areas of the breeds were similar, except for the smaller area of the Shorthorns. Fat thickness was less for breeds that had less marbling. In pork, the Duroc breed contained approximately one score more marbling than other breeds; however carcass weight, length and fat thickness was nearly the same for all the breeds. Greater quantities of marbling were significantly associated with smaller longissimus areas, a relationship not observed in beef. This difference in the two species studied may be the result of a difference in state of compositional maturity.