Research on the ovarian and follicular development in six months of age and adult yaks

To investigate the developmental condition of the ovary and ovarian follicles in six months of age and adult yaks,the length,width and thickness of the ovaries and their follicle numbers were compared,the effects of in vitro maturation of yak oocytes were also compared.The results showed that the ovarian length,width and thickness in adult yaks were significantly greater than that of in six months of the age in yaks(P0.05),the volume and weight in adult yaks were extremely significant higher than that of in six months of age in yaks(P0.01).ClassⅠ follicular number and average total numbers of follicles in six months of age in yaks were extremely significant higher than that of in adult yaks(P0.01),but class Ⅱ follicular number were not significantly different.Each of adult yaks contained(0.02±0.15) class Ⅲ follicle,but 6 months of age in yaks had no class Ⅲ follicles.The ovarian weight of adult yak with corpus luteum was significant higher than that of without corpus luteum.At the same time,the ovaries with corpus luteum contained(0.06±0.24) class Ⅲ follicle.The rates of in vitro maturation for class A and B oocytes were(81.39±3.53)% and(80.44±4.50)% in six months of age and adult yaks(P0.05),while the average oocytes number and average class A and B oocytes number of 6 months of age in yaks was significantly higher than that of adult yaks(P0.05).