Abstract:

In order to reveal the adaptation mechanism of skeletal muscle in yaks to hypoxia, DaTong yak at different age stages were selected, and cattle in plain field were selected as control at the same time. The average section area (Ax), average volume (V), the numerical density on area (N_A) and volume density (Vv, volume density of mitochondria in unit volume of skeletal muscle fiber) of mitochondria in skeletal muscle of Yak and cattle were compared by microstereolgy technology. Results showed that the average section area, average volume of mitochondria in skeletal muscle of DaTong yak declined at first and then increased from birth to adult, and there were significant differences between any two of the groups (P<0.05). The numerical density on area and the area density increased at first and then decreased from birth to adult, and notable differences can be find between any two of the groups (P<0.05). The volume density of skeletal muscle mitochondria in DaTong yaks increased following growth, and these parameters mentioned above in DaTong yaks were higher notably than those in plain cattle at the same age (P<0.01). According to the results, we can get the conclusions that skeletal muscle of DaTong yak have a perfect histoheredity characteristics at birth and have a fine adaptive ability to plateau hypoxia environment with characters including smaller muscle fiber diameter, larger surface area density and collagen fiber content, larger microvessel density, more tiny average volume, and higher mitochondria numerical density on area, higher mitochondria area density and higher mitochondria volume density. The structure of skeletal muscle changes continually to promote their growth and to adapt to the environment. Following growth, the muscle fiber diameter and mitochondria volume density increased, but surface area decreased gradually, collagen fiber content and mitochondria numerical density on area increased at first and then decreased, but microvessel density and mitochondria average volume declined at first and then increased. The 30th day of new born yak is a critical stage to get the ability of adaptation for external environment.