Skeletal Muscle Morphology Of Datong Yak At Different Development Stages

Da Tong yaks from plateau and cattles from plain at different development stageswere reseached to reveal the adaptation characteristic of yak to the plateau hypoxiaenvironment. Muscle fiber diameter, surface area density and collagen fiber contentof skeletal muscle were assayed by histological method, Microvessel density ofskeletal muscle was detected by histochemistry method, and mitochodria textureparameters were studied by electron microscopy technology. Results showed asfollows:1. Muscle fiber diameter of skeletal muscle in DaTong yaks and plain cattles icreasedsignificantly (P<0.01) but surface area density of skeletal muscle decreased strikingly(P<0.01) following growth.Fiber diameter of skeletal muscle in DaTong yaks was compared with that in plaincattles at the same ages. Results showed that skeletal muscle fiber diameter of yak at1-day-old,30-day-old, and adult were greater than those of cattles at the same ages,but the diameter of180-day-old yaks was smaller than that of180-day-old cattles.Compared with same age cattles, skeletal muscle surface area density were smaller at1-day-old yak,30-day-old yak, and adult yak, but greater at180day. These resultswere opposite to the results about fiber diameter.2. The content of collagen fiber in yak skeletal muscle at30days was higherobviously than that at1day and then descended gradually with a bottom drop at adult.The content of collagen fiber in plain cattle skeletal muscle decreased following thecattle growth. The content of collagen fiber in yak skeletal muscle was higherobviously than the same age cattles’(P <0.05).3. Change tendency of microvessel density of skeletal muscle in yaks was same asthat in cattles. Microvessel density was lowest at30day, then increased gradually andgot a peak at adult, not only in yaks but also in cattles. The differents were significantamong those groups (P <0.01). Microvessel density of yak skeletal muscle was higherstrikingly than the same age cattles’(P <0.01).4. The average section area, average volume of mitochondria in skeletal muscle of DaTong yaks declined at first and then increased from birth to adult, and there weresignificant differences between any two of the groups(P<0.05). The numerical densityon 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). Thevolume density of skeletal muscle mitochondria in DaTong yaks increased followinggrowth, and these parameter metioned above in DaTong yaks were higher notabllythan those in plain cattles at same age(P <0.01).In summary, Skeletal muscle of DaTong Yak have a perfect histohereditycharacteristics at birth and have a fine adaptive ability to plateau hypoxiaenvironment with characters including smaller muscle fiber diameter, larger surfacearea density and collagen fiber content, lager microvessel density, more tiny averagevolume, and higher mitochondria numerical density on area, higher mitochondria areadensity and higher mitochondria volume density.The structure of skeletal muscle changes continually to promote their growth and toadapt to the enviroment. Following growth, the muscle fiber diameter andmitochondria volume density increased, but surface area decreased gradually,collagen fiber content and mitochondria numerical density on area increased at firstand then decreased, but microvessel density and mitochondria average volumedeclined at first and then increased. The30th day of new born yak is a critical stage togot the ability of adaptation for external environment.