Long term effects of Ovum Pick-up (OPU) on reproductive activity of buffalo cows (Bubalus bubalis).

OPU has been previously carried out in buffalo species for a period as long as four months in our group. The aim of this work was to evaluate the long-term effects of OPU sampling on the reproductive status of the donors. The trial was performed on eight dry buffalo cows for 9 months. Sampling was performed twice a week in the first 91 days of the trial and once a week for the remaining months, due to a slowing down of the follicular growth. Cumulus-enclosed oocytes (COCs) were morphologically selected according to their quality (A to D). COCs were in vitro matured, fertilized and cultured with our standard procedures. ANOVA was used for statistical analysis. It was possible to distinguish a first period of 6 months characterized by blastocyst production followed by an unproductive period of 3 months during which embryos were not produced. During the first 6-months a higher number of follicles (5.0 vs 3.76; P<0.01), total COCs (2.56 vs 1.57; P< 0.01) and good quality (A+B) oocytes (1.51 vs 0.92; P<0.01) per subject/session were recorded compared with the last 3 months. Furthermore 0.35 blastocysts were obtained per buffalo/session during the first period whereas no blastocysts were produced in the last one (P>0.05). These findings may be accounted for by a functional exhaustion of the follicular pool after repeated OPU for extended time. Further studies are needed to confirm this hypothesis.