Meiotic and developmental competence of prepubertal and adult swine oocytes

The present study was conducted to compare meiotic and cytoplasmic competence of prepubertal and adult porcine oocytes, and the effects of EGF (0 to 100 ng/mL), FSH (0 to 400 ng/mL) and prepubertal pFF (0 to 10%) on nuclear maturation. Prepubertal oocytes were less responsive to FSH and pFF than were adult oocytes in terms of stimulation of nuclear maturation. The best nuclear maturation rates for prepubertal oocytes were obtained with 10 ng/mL EGF and 400 ng/mL FSH, whereas for adult oocytes no additional effect of EGF was seen in the presence of 400 ng/mL FSH. Supplementation with pFF had no additional effect on MII yield over that obtained with EGF plus FSH. After maturation in the presence of EGF, FSH and cysteamine, fertilization rates were not different between adult and prepubertal oocytes, but polyspermy was more frequent in prepubertal oocytes (31 +/- 17% vs. 17 +/- 7% in prepubertal and adult oocytes, respectively, P < 0.05). The addition of pFF to maturation medium decreased oocyte fertilization of adult oocytes and polyspermic fertilization in prepubertal oocytes. Blastocyst yield and developmental competence were significantly reduced in prepubertal oocytes compared to adult oocytes. The mean cell numbers in blastocysts cultured for 7 days ranged from 61 to 74, and did not differ among groups. Finally, the viability of the 2- to 4-cell embryos and blastocysts produced was assessed by embryo transfer experiments. One offspring was obtained after transfer of 2- to 4-cell embryos, and one after transfer of in vitro-produced blastocysts. In conclusion, although prepubertal gilt oocytes appeared less meiotically and developmentally competent than their adult counterparts, they can be used to produce blastocysts able to develop to term.