Maturation in vitro of calf and cow oocytes

The aim of the present study was to compare the morphology of the ovaries and the capacity for in vitro maturation of oocytes collected from 1-2-month-old calves and adult cows that were not hormonally stimulated. The study was performed on the ovaries of slaughtered diary and cross-beef calves (n=24) and adult cows (n=22). The mean weight of a calf and an adult cow ovary was 1.6 +/- 0.6 g and 8.5 +/- 2.9 g respectively (p<0.01). Comparable numbers of oocytes were dissected from the ovaries of calves and cows that had not been hormonally stimulated, from which about 50% proved to be capable of in vitro culture. During the 24 hour in vitro culture both calf and cow oocytes demonstrated a similar capacity for in vitro maturation. However, calf oocytes were smaller in diameter then the oocytes of adult cows which seems to suggest that they are less capable of embriogenesis.