A viable foal obtained by equine somatic cell nuclear transfer using oocytes recovered from immature follicles of live mares.

The presence of heterogenous mitochondria from the host ooplast affects the acceptance of offspring obtained by somatic cell nuclear transfer. This might be avoided by obtaining oocytes from selected females, but is then complicated by low numbers of available oocytes. We examined the efficiency of equine somatic cell nuclear transfer using oocytes recovered by transvaginal aspiration of immature follicles from 11 mares. Use of metaphase I oocytes as cytoplasts and of scriptaid (a histone deacetylase inhibitor) treatment during oocyte activation were evaluated to determine if these approaches would increase blastocyst production. In experiment 1, blastocyst development was 0/14 for metaphase I oocytes and 4/103 (4%) for metaphase II oocytes. Three blastocysts were transferred to recipient mares, resulting in two pregnancies and one live foal, which died shortly after birth. In experiment 2, blastocyst development was 2/47 (4%) for control oocytes and 1/83 (1%) for scriptaid-treated oocytes. No foals were born from two blastocysts transferred in the control group. The blastocyst from the scriptaid treatment resulted in birth of a live foal. In conclusion, this is apparently the first report of production of a viable cloned foal from oocytes collected from immature follicles of live mares, supporting the possibility of cloning using oocytes from selected mares.

Evaluation of foal production following intracytoplasmic sperm injection and blastocyst culture of oocytes from ovaries collected immediately before euthanasia or after death of mares under field conditions.

OBJECTIVE: To evaluate the efficiency of foal production following intracytoplasmic sperm injection (ICSI) and blastocyst culture of oocytes from mares that died or were euthanized under field conditions. DESIGN: Prospective case series. ANIMALS: 16 mares (age, 3 to 19 years) that died or were euthanized for various causes. PROCEDURES: Ovaries were collected immediately before euthanasia (n = 10) or after death (6). Ovaries were transported to the laboratory for oocyte recovery (15 mares), or oocytes were recovered at a remote location and shipped to the laboratory (1). Oocytes underwent ICSI, and presumptive zygotes were cultured for 7 to 10 days. Blastocysts were shipped to embryo transfer facilities for transcervical transfer to recipient mares. RESULTS: Ovaries were processed 30 minutes to 12 hours (mean ± SD, 4.6 ± 3.3 hours) after mares' deaths. A mean of 14.1 ± 8.6 oocytes/mare were cultured, and 110 of 225 (49%) matured. Twenty-one blastocysts developed after ICSI and were transferred to recipient mares. Thirteen pregnancies were established; 10 healthy foals were produced from 6 donor mares. The number of blastocysts produced per mare and number of live foals produced per mare were significantly correlated with the number of oocytes recovered. CONCLUSIONS AND CLINICAL RELEVANCE: Foals were produced from mares after death or euthanasia under field conditions. Proportions of foals born overall (10 foals/16 mares) and mares from which ≥ 1 foal was produced (6/16) were greater than those reported following recovery and oviductal transfer of oocytes to inseminated recipients after death of donor mares under field conditions.