Long term effect of Ovum Pick-up in buffalo species

Abstract

The aim of this study was to evaluate the effect of an Ovum Pick-up (OPU) treatment carried out for 9 months in buffalo (Bubalus bubalis) species. Eight pluriparous non-lactating buffalo cows underwent OPU for 9 months. Recovered cumulus enclosed oocytes (COCs) were classified and COCs suitable for in vitro embryo production (IVEP) were in vitro matured (IVM), fertilized (IVF) and cultured (IVC) to the blastocyst (Bl) stage. Animals were monitored for a total period of 270 days, but at the summer solstice, follicular turnover decreased and at the 68-day of the trial, we decided to increase the OPU sampling interval from 3-4 to 7 days. It was therefore possible to distinguish two phases: a first phase (18 sessions), during which OPU was carried out twice weekly and a second phase (16 sessions) during which OPU sessions were performed weekly. This reduction did not modify the percentage of good quality COCs, while the incidence of grade D COCs decreased (P<0.01). Furthermore, embryo production was higher in the second phase, either if embryos were calculated on the total recovered COCs (8.3% vs. 21.4%; P<0.01) and on grade A+B COCs (13.0% vs. 32.1%; P<0.01), that supposedly should have given similar blastocyst yield. During the total period of the trial it was possible to distinguish a first period of 6 months (34 sessions) characterized by blastocyst production (0.36 blastocyst/buffalo/session), followed by an unproductive period of 3 months (12 sessions), during which embryos were not produced. During the first 6 months a higher (P<0.01) number of follicles (5.06 vs. 3.71), small follicles (3.38 vs. 2.07), total COCs (2.58 vs. 1.56) and good quality (A+B) COCs (1.51 vs. 0.94) per subject/session were recorded compared to the last 3 months. No Blastocyst were produced during the second period, even if the percentage of grade A+B COCs was similar to that recorded during the first period. In conclusion, buffalo cows submitted to repeated OPU sampling for a 9-month period, showed a decline of follicle recruitment and oocyte collection after the first two months of samplings. After 6-month of samplings, in spite of the quality grade of the collected oocytes, we found a drop in their developmental competence.