Abstract: The objective of this study was to investigate the effects of grazing in nature pasture and fattening in house on meat quality, nutritional components of yaks in cold season. Theoretical data has been provided for evaluating the quality of yak meat nutritional regulation of short-term fattening in cold season. A total of 12 5-year-old healthy and no disease male yaks with similar body weight ((270±10) kg) were selected. The yaks were randomly divided into 2 groups:grazing and barn feeding fattening groups, 6 replicates in each group. At the same time, the animals were grazed in nature pasture and fattened in house with total mixed rations (TMR), respectively, the test period was 120 days. At the end of the fattening trial, the two groups of yaks were slaughtered and 500 g of longissimus dorsi (LD), biceps brachii (BB) and biceps femoris (BF) were collected, respectively, for the determination of meat quality (processing quality and edible quality) and nutritional components. The results showed that:1) After barn feeding fattening, the meat color luminance values(L^*) of the 3 parts significantly improved (P<0.05), however, the redness values (a^*) were significantly decreased(P<0.05); The water loss rate of LD was significantly decreased(P<0.05), and the water loss rate of BB and BF were extremely significantly decreased(P<0.01);The cooking loss and shear force of LD were extremely significantly decreased(P<0.01); The cooking loss and shear force of BB and BF were significantly decreased(P<0.05). 2) The effect of fattening in house on contents of moisture, protein, fat, calcium and phosphorus in different parts of yak muscle were extremely significant (P<0.01); However, the ash content was only significantly affected in LD (P<0.01). 3) The contents of essential amino acids (EAA) and non-essential amino acids (NEAA) in LD were significantly affected by fattening in house(P<0.05), while the contents of essential amino acids (EAA) and non-essential amino acids (NEAA) in other two parts of muscle had no significant change(P>0.05); In the three parts of muscle, the main fatty acids were C_16:0, C_18:0, C_18:1N₉C, C_18:2N₆C and C_20:4N₆; The content of polyunsaturated fatty acids (PUFA) in each part of muscle was extremely significantly decreased (P<0.01), the content of monounsaturated fatty acids (MUFA) was extremely significantly increased (P<0.01), and the ratio of n-6/n-3 was decreased in each part of muscle. The results indicated that, compared with natural grazing, the luminance and the redness of yak meat were affected by fattening in house, the processing quality of yak meat was improved, the cooking loss was reduced, at the same time, the general nutritional components of yak meat were higher than that of grazing yak. The amino acids composition and protein quality in longissimus dorsi of fattening yaks were better than that of grazing yaks. Fattening in house sacrifices some rich, healthy fatty acids in muscle, but the fat content increased, which can greatly improve the edible quality and tenderness of yak meat.

Key words: yak, meat quality, nutritional value, grazing, short-term fattening