Abstract: The feeding system is one of the important factors affecting yak meat quality. The purpose of this study was to compare the effects of two different feeding modes on the rumen microflora, meat quality and flavor substances of yaks. A total of 16 yaks with similar age and body mass in two feeding systems (grazing and feedlot, 8 animals each) were slaughtered. Rumen fluid was collected for microbial community diversity analysis and Longissimus dorsi muscle was harvested for the determination of meat quality, fatty acid composition, muscle fiber characteristics and volatile flavor substances. The results showed that the number of operational taxonomic units (OTU), the richness indices ACE and Chao 1, and Shannon index of rumen microorganisms in grazing yaks were significantly higher than those in feedlot yaks (P < 0.05). The meat quality traits dripping loss, cooking loss, cooked meat shear stress and muscle fiber density of feedlot yaks were significantly lower than those of grazing yaks (P < 0.05). Meanwhile, the intramuscular fat content was 1.14 g/100 g, which was significantly higher than that of grazing yaks (P < 0.05). The contents of saturated fatty acids and monounsaturated fatty acids in the muscle of feedlot yaks were significantly higher than those in grazing yaks (P < 0.05), while the content of polyunsaturated fatty acids was significantly lower than that in grazing yaks (P < 0.05). Thirty-four and twenty-seven volatile flavor substances were detected in the muscles of grazing and feedlot yaks, respectively. In summary, the meat quality of feedlot yaks was better than that of grazing yaks, whereas the fatty acid composition of muscle lipids was inferior to that of grazing yaks, possibly due to the difference in rumen microfloral diversity between the two feeding systems. This study provides a scientific basis for the feedlot finishing of yaks to produce a plentiful variety of yak meat products.

Key words: feeding system, rumen microorganisms, meat quality, volatile flavor compounds