Morphokinetics of early equine embryo development in vitro using time-lapse imaging, and use in selecting blastocysts for transfer.

The use of time-lapse imaging (TLI) in the evaluation of morphokinetics associated with invitro developmental competence is well described for human, cattle and pig embryos. It is generally accepted that embryos that complete early cleavage sooner are more likely to form blastocysts and that timing of later events, such as blastocyst formation and expansion, are predictive of implantation potential and euploid status. In the horse, morphokinetics as a predictor of developmental competence has received little attention. In this study we evaluated the morphokinetics of early equine embryo development invitro for 144 oocytes after intracytoplasmic sperm injection and report the timings of blastocyst development associated with ongoing pregnancy for the first time. There was a tendency for time of cytoplasmic extrusion and first cleavage to occur earlier in the embryos that went on to form blastocysts (n=19) compared with those that arrested, and for first cleavage to occur earlier in blastocysts that established pregnancies that were ongoing (n=4) compared with pregnancies that were lost (n=2). TLI was clinically useful in identifying blastocysts when evaluation of morphology on static imaging was equivocal.

Induction of ovulation in seasonally anestrous mares under ambient lights using recombinant equine FSH (reFSH).

Traditionally, mares are put under artificial lights to advance the first ovulation of the year. The aim of the present study was to determine the efficacy of recombinant equine FSH (reFSH) in stimulating follicular development and advancing the first ovulation of the year in seasonally anestrous mares compared with anestrous mares given a placebo. Both groups of mares were housed under ambient light conditions. Sixty deep anestrous mares of light horse breeds (follicular diameters ≤ 20 mm in diameter and progesterone <1 ng/mL) were maintained under a natural photoperiod at three different sites: University of California, Davis, Colorado State University, and University of Kentucky Gluck Centre. Twenty mares at each site were randomly allocated to receive either 0.65 mg of reFSH (group A: treatment; n = 10) or a placebo (group B: control; n = 10) twice daily by im beginning on January 31. Treatment continued until one or more preovulatory follicles developed or up to a maximum of 15 days. Randomized treatments were blinded. Follicular development was closely monitored by transrectal ultrasonography. When the largest follicle reached ≥ 35 mm in diameter, reFSH treatment was discontinued and an injection of 2500 international units of hCG was administered iv 36 hours later to induce ovulation. Jugular blood samples were collected daily from all mares at University of California, Davis, and processed for LH, FSH, progesterone, estradiol-17ß, and immunoreactive-inhibin by RIA. All 30 mares receiving reFSH (group A) developed follicles ≥ 35 mm within 7.4 ± 1.6 days of treatment. Twenty-three of the 30 reFSH-treated mares (group A) ovulated within 72 hours after hCG administration. In contrast, mares in group B (placebo, control) did not exhibit significant follicular development and none ovulated within the 15-day observation period. Mares in group A had significantly higher plasma levels of FSH, estradiol-17ß, and immunoreactive-inhibin during treatment but did not exhibit a preovulatory LH surge. Mares administered reFSH returned to anestrus and spontaneously ovulated at a similar calendar date as control mares. These data indicate that reFSH was effective in stimulating the development of ovarian follicles and advancing the first ovulation of the year in seasonally anestrous mares under ambient lights but was not successful in inducing continued cyclicity.