Abstract: Taking the 4.5-year-old male yaks and yak-cattles in Xiaojin county as the research object, which were treated by house feeding and grazing feeding. After slaughter, the muscles of the longissimus dorsi, triceps and biceps of the yak, yak and grazing calves are collected to measure the muscle fiber diameter, muscle fiber density, intramuscular muscle fiber content, and intramuscular connective tissue content. The results showed that the muscle fiber diameter and intramuscular muscle fiber content of the yak, yak-cattles and grazing yaks were not significantly different among the three muscle parts; the muscle fiber density of the triceps of the house feeding yak was significantly higher than that of the biceps femoris; the intramuscular connective tissue content of the longissimus dorsi and triceps of the house feeding yak-cattles was significantly higher than that of the biceps femoris; The muscle fiber density of the grazing feeding yaks and yak-cattle, and the intramuscular connective tissue content of the house breeding and grazing yak were not significantly different among the three muscle parts; the intramuscular muscle fiber content and intramuscular connective tissue content of the muscles in the three parts were not significantly different between the house breeding yak, house breeding yak-cattle and the grazing yak; the muscle fiber diameter of the longissimus dorsi of the house feeding yak was significantly higher than that of the house feeding yak-cattle; the muscle fiber diameter of the biceps femoris of the house feeding yak was significantly higher than that of the grazing yak. There was no significant difference in the muscle fiber diameter of the triceps muscles. The difference in muscle fiber density of the triceps was extremely significant.

Key words: house feeding yak, diameter of muscle fiber, density of muscle fiber, intramuscular fiber content, intramuscular connective tissue content