Intrafollicular oocyte transfer in the horse: effect of autologous vs. allogeneic transfer and time of administration of ovulatory stimulus before transfer.
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PURPOSE: To assess meiotic and developmental competence after transfer of immature cumulus-oocyte complexes (COCs) to the preovulatory follicles of mares (intrafollicular oocyte transfer (IFOT)). METHODS: In Experiment 1, mares received an ovulatory stimulus at IFOT. Thirty hours later, COCs were recovered from the follicle, and mature oocytes underwent ICSI and embryo culture. In Experiments 2 and 3, autologous vs. allogeneic COCs were used. The mares were inseminated and embryos were recovered. In Experiment 3, the ovulatory stimulus was administered 9h (autologous) and 15h (allogeneic) before IFOT. In Experiment 4, only allogeneic COCs were used; the ovulatory stimulus was administered 9 or 15h before IFOT. Excess embryos (autologous) and parentage-verified embryos (allogeneic) were considered IFOT-derived. RESULTS: In Experiment 1, 36/54 IFOT oocytes (67%) were recovered, of which 56% were mature, vs. 49% of in vitro matured oocytes (P>0.1). After ICSI, blastocyst rates were 25% and 18%, respectively (P>0.1). In Experiment 2, 0/6 autologous and 2/6 allogeneic IFOT yielded IFOT-derived embryos. In Experiment 3, 0/7 autologous and 2/5 allogeneic IFOT yielded IFOT-derived embryos. The proportion of mares yieldingIFOT-derived embryos was lower after autologous vs. allogeneic IFOT (0/13 vs. 4/11; P<0.05). In Experiment 4, 1/8 9-h and 1/7 15-h IFOT yielded IFOT-derived embryos. CONCLUSIONS: Transferred oocytes mature within the follicle and can maintain developmental competence. Allogeneic IFOT was more efficient than was autologous IFOT. The time of ovulatory stimulation did not affect embryo yield. The IFOT procedure is still not repeatable enough to be recommended for clinical use.
