Culture of horse oocytes in vitro.

Oocytes were removed from follicles 5-30 mm in diameter. The germinal vesicle was present in 69.6% (23/33) of the oocytes at the start of culture, but after 20-24 and 40 h 70.5% (12/17) and 68.2% (43/63) of the oocytes were in metaphase I and metaphase II with first polar body extruded, respectively.