A new evaluation method of marbling fineness in M. longissimus thoracic of Japanese Black Cattle

In recent years, marbling fineness has been attracted attention for the evaluation of meat quality of Japanese Black cattle, and it must be converted into the numerical value. Therefore, we examined several image analysis methods for objective evaluation of marbling fineness, and estimated its genetic parameters. Thirty Japanese Black cattle, various shape of the rib eye area and of marbling, were used in this study. The carcass images were captured from the 6-7th rib cross section. To determine visual evaluation values of marbling based on the fineness, five skilled panelists allocated for the carcass assessment. Six different calculations, the sum of circumferential lengths of marbling particles which were obtained by image analysis, for the new evaluation methods of marbling fineness were examined, and correlation analysis with visual evaluation values were conducted. Data for genetic analysis were collected from the Japanese Black cattle (n = 25,432) listed on the carcass market in Hokkaido between September 2005 and July 2018. The range of rib eye area and beef marbling standard (BMS) for the thirty selected rib eyes were 55 to 121 cm2 and 10 to 12, respectively. The correlation coefficient between the visual evaluation values and the values obtained by dividing the sum of circumferential lengths of marbling particles by the area of the rib eye area (NFI-2) was the strongest correlation (−0.81). The heritability of NFI-2 was 0.55, which indicated that the trait for which genetic improvement might be sufficiently possible.