Abstract: Analysis fatty acid composition in muscle of Jiulong and Angke two yak breed and Xuanhan,Pingwu,Chuannan,Ebian four yellow cattle breed. Meat fat was separated and the fatty acid composition was analyzed using GC-MS following methyl esterification. The results demonstrated that the sixteen varieties fatty acid there are significant difference except stearic acid (p<0.05) in different varieties. The content of unsaturated fatty acid there is great difference from 18.65% to 3.07% in different varieties. The contents of unsaturated fatty acid in yak (48.49%) is obviously higher than yellow cattle (41.87%), the highest is the Jiulong yak (49.40%); There exists the significant difference of polyunsaturated fatty acid among different varieties, the highest is in the Jiulong yak (15.41%) and Pingwu yellow cattle(15.72%), The ratio of MUFA/PUFA is 3.69:1in Jiulong yak and 2.53:1 in Pingwu yellow cattle. The results indicated that Jiulong yak has high nutritional value, this has the important meaning to the development of Jiulong yak and breeding of cattle.

Key words: yak, yellow cattle, fatty acid, longissimus dorsi, GC-MS