Embryo recovery rate following superovulation with equine pituitary extract (eFSH®) in mares

Embryogewinnungsrate nach Superovulation mit equinem Hypophysenextrakt (eFSH®) bei der Stute

Köllmann M, Probst J, Baackmann C, Klewitz J, Squires E S, Sieme H

DOI: 10.21836/PEM20080310
Year: 2008
Volume: 24
Issue: 3
Pages: 397-405

Embryo recovery from single ovulating mares is approximately 50% per estrous cycle, leading to a non-economical state of embryo transfer in the mare. An ability to consistently induce multiple follicles and ovulations in estrous cycling mares would enhance embryo recovery from donor mares, provide multiple follicles for collection of oocytes, and improve pregnancy rates from subfertile mares. There have beennumerous approaches to superovulation of the mare. Injections of porcine FSH, inhibin vaccines, equine chorionic gonadotropin (eCG) and GnRH have been of limited success in stimulating multiple ovulations in the mare. Numerous studies have shown that injection of equine pituitary extract (EPE) will result in three to four ovulations per estrous cycle and two embryos. Recently, a commercial purified equine pituitary extract product (eFSH®) has been available. In the present study six normally cycling mares were investigated over five cycles and ovulation rate and embryo recovery rate were compared between control cycles and stimulated cycles. Cycle one and three were designed as control cycles without stimulation and insemination. In cycles 2 and 4 mares were treated with 12.5 mg eFSH® intramuscularly twicedaily beginning when the diameter of the largest follicle was 20 to 25 mm. Prostaglandin was administered on the second day of eFSH® therapy. Treatment with eFSH® was continued until follicle(s) were 32-35 mm in diameter. The mares were subsequently allowed to ‘coast’ for 36 h, after which 2500 IU human chorionic gonadotropin were administered to induce ovulation. Mares were inseminated with 750 Mio. progressive motile sperms of a fertile warmblood stallion. Embryo recovery was performed 6.5 days following ovulation. In the last cycle (5) mares were treated and inseminated in the same way than in cycle 2 and 4, but without eFSH® stimulation. Ovulation rate in control cycles was lower (1.3 ovulations) than in eFSH® treated cycles (4.4 ovulations). The number of days of eFSH® treatment required forreaching a follicle size of 32-35 mm was on average 4,0 days. Embryo recovery rate in control mares was 1.2 per cycle, whereas in eFSH® treated mares ø 2.9 embryos could be flushed. The eFSH® protocol used in this study was efficient to induce multiple ovulations and increase embryo recovery rate in mares. Nevertheless the number of embryos obtained is quite encouraging, individual mare variation is considerable. Being able to identify donor mares that respond favorably to eFSH based on follicular development, ovulation and embryo recovery would be a great advantage. In current studies a possible influence of follicle development and genital blood flow on embryo recovery rate is investigated to identify „good donor mares“ in a superovulation program.