Meiotic and developmental competence of prepubertal and adult swine oocytes

The present study was conducted to compare meiotic and cytoplasmic competen ce of prepubertal and adult porcine oocytes, and the effects of EGF (0 to 1 00 ng/mL), FSH (0 to 400 ng/mL) and prepubertal pFF (0 to 10%) on nuclear m aturation. Prepubertal oocytes were less responsive to FSH and pFF than wer e adult oocytes in terms of stimulation of nuclear maturation. The best nuc lear maturation rates for prepubertal oocytes were obtained with 10 ng/mL E GF 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 w as more frequent in prepubertal oocytes (31 +/- 17% vs. 17 +/- 7% in prepub ertal and adult oocytes, respectively, P < 0.05). The addition of pFF to ma turation medium decreased oocyte fertilization of adult oocytes and polyspe rmic fertilization in prepubertal oocytes. Blastocyst yield and development al competence were significantly reduced in prepubertal oocytes compared to adult oocytes. The mean cell numbers in blastocysts cultured for 7 days ra nged 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 embry o 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 an d developmentally competent than their adult counterparts, they can be used to produce blastocysts able to develop to term. (C) 2001 by Elsevier Scien ce Inc.