1MVSc Student in Animal Reproduction, Department of Animal Reproduction, Gynaecology and Obstetrics, Faculty of Veterinary Sciences and Animal Husbandry Sher-e-Kashmir, University of Agricultural Sciences and Technology of Kashmir, India
2Department of Animal Reproduction, Gynaecology and Obstetrics, Faculty of Veterinary Sciences and Animal Husbandry, Sher-e-Kashmir, University of Agricultural Sciences and Technology of Kashmir, Srinagar, Jammu and Kashmir, 190 006, India
A study was conducted to investigate the effect of follicular size (small, <2 mm diameter and large, ≥2 mm) on in vitro maturation, fertilization and culture of ovine oocytes. The ovaries (n=80) were collected from abattoirs in Srinagar city, India and transported in normal saline solution containing 50 μg gentamicin sulphate per ml in a thermos flask. The oocytes were collected by puncture technique and good and fair quality oocytes obtained were subjected to maturation in TCM-199 supplemented with epidermal growth factor (EGF) for 24 h under 5% CO2 and humidified atmosphere at 38.5°C. The matured oocytes were then subsequently subjected to fertilization and culturing was done for six days. The results revealed that the maturation rate of large follicle oocytes (85.20%) was higher than small follicle oocytes (52.44%, P=0.002). In vitro fertilization rates for small and large follicle oocytes were not significantly different (79.54 and 76.65%, respectively). However, cleavage and morula rates were higher in large follicle oocytes (58.69 and 34.13%) than small follicle oocytes (38.63 and 19.32%, respectively, P<0.05). In conclusion, there is higher developmental competence of oocytes from the large follicles than small follicles and the pre-maturation of oocyte occurring during follicular growth is essential for subsequent embryonic development in sheep.