Oocyte retrieval in superstimulated buffalo heifers.

Embryo production following oocytes in vitro fertilization is related on number of oocytes collected by Ovum pick-up. The objective of this study was to compare stimulated peripuberal buffaloes and to assess ovarian response and oocyte recovery. On day 0, 12 heifers undergone clinical examination of genital tract by ultrasound and a progesterone releasing intravaginal device was inserted into the animals. On day 3 buffaloes were divided into two treatment groups , according to their age, body weight and follicular population on day 0 and 3. On day 7 all buffaloes undergone ultrasound examination and number and size of the follicles was recorded. Heifers in Group A (n=6) received a 4-day decreasing dosage of an equal mixture of 500 I.U. of Follicle Simulating Hormone and 500 I.U. of Luteinizing hormone; Group B (n=6) received a single i.m. injection of Pregnant Mare Serum Gonadotrophin and a 2-day decreasing dosage of an equal mixture of 175 I.U. of FSH and 175 I.U. of LH, starting on day 5. Group B resulted in a significantly higher (P<0.05) number of large-very large follicles compared to group A (13.2 vs 8.3). Although no significant differences, in group A and B, were found on the number of observed follicles (14.2 vs 18.2), aspirated follicles (11.5 vs 14.0), recovered oocytes (6.33 vs 6.5) and percentage of recovered oocytes/aspirated follicles (60,0 vs 44.8), all the parameters tended to be higher in group A. The percentage of viable oocytes (3.2 vs 3.2) was similar. Protocol B stimulated the recruitment and the growth of a higher number of small follicles. It is possible to hypothise that the higher size of the follicles in group B, caused the lost of follicular fluid affecting oocyte recovery.