Effect of roscovitine pretreatment for increased utilization of small follicle-derived oocytes on developmental competence of somatic cell nuclear transfer embryos in pigs.

The objective of this study was to evaluate the effect of roscovitine pretreatment on the number of matured oocytes per ovary available for somatic cell nuclear transfer (SCNT) and their developmental competence. Irrespective of reproduction status (prepuberty/puberty), the average number of small follicles per ovary (19.3/17.2) was higher than that of medium follicles (1.5/2.7). In the small follicle group, the in vitro maturation rate of COCs pretreated with 50 µM roscovitine (56.1%) was significantly (P < 0.05) higher than that of the control, 25 or 75 µM treatment (15.5%, 23.7% and 35.2%, respectively), while, in the medium follicle group, there was no significant difference between the control, 25, 50 and 75 µM treatment (76.4%, 78.3%, 80.9% and 60.6%, respectively). As a result, a total number of matured oocytes per ovary was greater for 50 µM treatment (11.8) than for the control, 25 or 75 µM treatment (4.4, 5.0 and 6.3, respectively). In the small follicle group, COCs pretreated with 50 µM roscovitine showed dramatically increased blastocyst rate (16.0%) compared to the control (2.9%) (P < 0.05), whereas, in the medium follicle group, there was no significant difference between groups independent of roscovitine treatment (20.8 vs 23.0%). The cloning efficiency in the roscovitine-treated group was not significantly different from that in the control (2.6 vs 1.4%). In conclusion, the present study indicates that roscovitine treatment increased the number of matured oocytes per ovary available for SCNT and did not have any adverse effect on cloning efficiency in pigs.