The compositions of fatty acid and molecular species of triacylglycerol of subcutaneous fat of fattened Japanese Black, Japanese Shorthorn and Holstein steers were determined by gas chromatography. There were significant differences in heptadecanoic acid concentration among three breeds, and in six acid (myristic, myristoleic, palmitic, palmitoleic, anteiso-heptadecanoic and stearic acids) concentrations between two breeds of three breeds. The relationship between palmitic and oleic acid

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... rations was negative. The major molecular species of subcutaneous triacylglycerol were myristoyl (M)-palmitoyl (P)-oleoyl (O)-glycerol (MPO), PPO, P-Palmitoleoyl (Po)-O-glycerol ([PPoO]), P-stearoyl (S)-O-glycerol (PSO) and POO. POO had the highest concentration in these molecular species of three breeds. Japanese Black had higher concentrations of PSO and SOL than those of Holstein. Relationships between POL and POO, and PPO and POO were positive and negative, respectively. In order to analyze the association of total lipid content of M longissimus thoracis and molecular species composition of triacylglycerol, multiple regression analysis was carried out. In the linear multiple regression analysis, the regression equation of Japanese Black had a good multiple correlation coefficient (0.8110). In discriminant analysis of samples separated according to meat quality score of carcass, the percentage of discrimination were 100% for each group of Japanese Black and Japanese Shorthorn.