Superovulation, embryo recovery, and pregnancy rates from seasonally anovulatory donor mares treated with recombinant equine FSH (reFSH).
Roser, J. F., Etcharren, M. V., Miragaya, M. H., Mutto, A., Colgin, M., Losinno, L. and Ross, P. J.
Department of Animal Science, University of California, Davis, CA, USA.
Facultad de Agronomia y Veterinaria, Universidad Nacional de Rio Cuarto, Argentina.
Facultad de Ciencias Veterinarias, INITRA, Universidad de Buenos Aires, Argentina.
Instituto de Investigaciones Biotecnologicas, Universidad Nacional de General San Martin, Argentina.
Aspen Bio Pharma Inc., Castle Rock, CO, USA.
Department of Animal Science, University of California, Davis, CA, USA. Electronic address:
The effectiveness of different treatments with recombinant equine FSH to stimulate follicular growth, multiple ovulations and embryo production in seasonally anovulatory mares was evaluated. During mid-winter season (July-August in Argentina, South America) forty light breed donor mares, presenting follicles <10mm in diameter and no CL at ultrasound examination (deep-anestrus), were randomly assigned (n=10/group) to one of the following treatments: Group 1: twice daily intramuscular (IM) injections of 0.65mg reFSH (AspenBio Pharma, CO), Group 2: once daily IM injection of 1.3mg reFSH, Group 3: twice daily IM injection of 0.32mg reFSH, and Group 4: once daily IM injection of saline (control). Treatment was administered until a follicle of 35mm was observed or for a total period of 10 days. When the largest follicle reached >/=35mm in diameter, treatment was discontinued and 2500 IU hCG was injected intravenously (IV) 36h later. Mares receiving hCG were inseminated with fresh semen every 48h until ovulation(s) were detected or one dose of frozen semen (250x10(6) motile sperm) after the first ovulation was detected. Eight days after first ovulation, transcervical embryo recovery was performed. Recovered embryos were non-surgically transferred to anovulatory estrogen/progesterone treated recipients and pregnancy diagnosed by ultrasonography 7, 14 and 21 days later. All mares receiving reFSH, but none receiving saline control, responded to the treatment with follicular growth. On average, 6.5 days of reFSH treatment were required for mares to develop follicles of ovulatory size (>35mm). Ovulations were detected in 80% of mares in Groups 1 and 2, 50% of mares in Group 3 and in none of Group 4 (Control). Among ovulating mares, no differences in number of ovulations, number of embryos recovered, or pregnancy rates were observed among reFSH treatments. Of treated mares, 6, 7, and 5 produced embryos in Groups 1, 2, and 3, respectively. The average embryo recovery rate per ovulated mare was 88%. The average embryo recovery rate per ovulation was 43%. Overall, a 59% pregnancy rate was achieved. These results indicate that treatment with reFSH during deep anestrus results in follicular development, ovulation of fertile oocytes, and production of embryos that established viable pregnancies after transfer. Also, a single daily administration of reFSH was as effective as two daily administrations, which allows for a simplified administration regimen.
Theriogenology 142: 291-295 (2020)