Comparison of regional differences of marbling distribution in rib eye among Japanese Black, Japanese Brown, Japanese Black×Holstein and Holstein cattle using image analysis

The purpose of this study was to compare regional differences of marbling distribution in the rib eye among Japanese Black, Japanese Brown, Japanese Black×Holstein and Holstein cattle using image analysis. Digital images of the rib eye on carcass cross sections were taken between the 6th and 7th ribs with mirror type photography equipment. These images were divided into four quadrants by inertia main axes. The following were calculated for each quadrant of the rib eye as well as the whole : marbling percent (MP), coarseness index of larger 5 marbling particles (CIM 1∼5), fineness index of marbling (FIM), average of luminance of lean (ALL) and average luminance of marbling (ALM). Coefficients of variation (CVs) between least square means of the 1-4 quadrants of image analysis traits were treated as marbling arrangement indicators, and these values were compared among breeds. MP of whole rib eye in Japanese Black (42.88%) was the highest, while those of Japanese Brown (32.82%) and Japanese Black×Holstein (33.65%) were similar at a moderate level, and MP in Holstein (22.33%) was the lowest. MP of the 1st and 4th quadrants were higher than those of the 2nd and 3rd quadrants for all breeds. However, CV of MP in Holstein (10.77) and Japanese Black×Holstein (4.63) were higher than other breeds (1.97-1.99). These results indicated that the marbling arrangement of rib eye in Holstein was relatively off balance. CIM 1-5 of the 3rd and 4th quadrants were higher than those of the 1st and 2nd quadrants in all breeds. In contrast, FIM of the 1st and 2nd quadrants were higher than those of the 3rd and 4th quadrants in all breeds. CV of CIM 1-5 of Holstein was the highest among breeds (40.77). Tendencies of characteristics of marbling arrangement in the rib eye were similar in all breeds, while degrees of bias for marbling distribution different for all breeds.