The aim of this study was 2-fold: (1) To determine if altrenogest-treated mares will yield higher numbers of quality in vitro-matured (IVM) oocytes than early pregnant mares and cycling/control mares and (2) if the addition of human follicular fluid (HFF) to IVM medium can support IVM and viable pregnancies from in vitro-produced blastocysts. In this study, 18 mares were assigned to 3 equally sized treatment groups and each mare was subjected to follicle aspiration every 10 to 11 days without monitoring follicular growth. The 3 treatment groups were altrenogest-treated mares (0.044 mg kg–1 of PO daily), early pregnant mares (30–110 days) and control/cycling mares. Using transvaginal ultrasound guidance, all visible follicles were aspirated. Altrenogest-treated mares each yielded more follicles (8.75) per aspiration session when compared with the control mare group (5.75) and the pregnant mare group (3.72), but there was no difference in oocyte recovery rates among the groups (Table 1). A limited number of these oocytes were subjected to in vitro maturation. After heated (38.5°C) transport of oocytes to an off-site laboratory, the oocytes were placed in maturation medium containing 10% HFF obtained from preovulatory follicles after ovulation induction, 20% serum substitute supplement and no hormones for 36 h. This approach yielded a maturation rate of 61.8, 68.8 and 82.0% for the altrenogest, pregnant and control treatment groups, respectively (not significant). Mature oocytes (n = 65) were injected with frozen-thawed sperm using a standard intracytoplasmic sperm injection (ICSI) technique. Four expanding blastocysts (Table 1) were selectively transported back to the embryo transfer facility and transcervically transferred into recipient mares on Day 6 post-ICSI. These 4 transfers resulted in 2 viable, normally progressing pregnancies, ongoing beyond 60 days of gestation. Both pregnancies resulted from the altrenogest-treated aspiration group. In this study we concluded that (1) altrenogest-treated mares provide more follicles and may be a better source of viable immature oocytes for the production of ICSI embryos and foals, but their overall advantage is unclear; (2) addition of HFF to IVM media, in the absence of added gonadotropins, can support oocyte maturation, blastocyst production and viable pregnancies; (3) an aspiration schedule of every 10 to 11 days without ultrasonic monitoring can yield viable immature oocytes, capable of producing ICSI blastocysts, resulting in viable pregnancies.
Table 1.Altrenogest-treated mares compared to early pregnant mares and control mares
The proteomics of human follicular fluid on the day of oocyte retrieval in in vitro fertilization cycle
