In vitro maturation of cattle oocytes taken from ovaries with different morphofunctional states

We studied the capacity of cattle oocytes taken from ovaries with different morphofunctional state for development to metaphase 2 in vitro. A classification of ovaries has been proposed according to their morphofunctional state: (1) ovaries with a yellow body from the last cycle, without dominating follicle, with many follicles of varying diameter; (2) ovaries with a yellow body from the last cycle, with dominating follicle (from 10 mm in diameter); (3) ovaries with a large functioning yellow body and follicles of varying diameter; (4) ovaries with a follicular cystoid formation (more than 25 mm in diameter); (5) ovaries with a yellow body from past cycles and small (1-2 mm) follicles, supposedly with a weakened hormonal function. It was shown that the morphofunctional state of ovaries determined the total number of oocytes isolated from an ovary and number of morphologically normal oocytes feasible for cultivation. At the same time, no reliable differences in the capacity for extrusion of the first polar body between the oocytes from the ovaries of different types were found in the experiments on in vitro oocytes maturation. Since the coefficient of correlation between the extrusion of the first polar body and maturation to metaphase 2 was in 0.95, there is every reason to believe that the capacity for development to metaphase 2 does not depend on the morphofunctional state of ovaries.