Effect of breeding season on development, viability, growth and diameter of oocytes in ewes.

摘要

We report effect of breeding on oocyte development, viability, diameter and percentage fully grown in ewes. Oocytes were aspirated from ovaries during breeding and non-breeding seasons to evaluate embryo development and from primordial, primary, secondary and antral follicles for diameters. Growth was assessed by brilliant cresyl blue stain. We found no effect of breeding on blastocysts (~18.0%). However, breeding boosted (P<0.05) diameter of antral oocytes (156.4 mum) compared with non-breeding season (153.9 mum) and increased from 16.2 mum in primordial follicle to 151.4 mum in early and 157.7 mum in late antral follicles. We found no effect of breeding with mature oocytes (~61.0%). Results suggest that pre-antral to early antral follicle transition is critical for oocyte diameter whereas breeding only affects it during antral stages. Despite variation in diameter we found no effect of breeding on fully grown oocytes or embryo growth.