Nonsurgical Embryo Transfer in a Private Practice (1998)

1. Introduction

Embryo transfer has become an important reproductive tool in many equine breeding programs throughout the world today. It is commonly utilized to produce multiple foals in a season from a particular mare, to produce foals from mares involved in some other activity such as showing or racing, and to produce foals from mares otherwise unable to successfully carry a foal to term. Surgical embryo transfer via flank laparotomy has been accepted as providing higher pregnancy rates than other methods, with an anticipated 75–80% of transfers resulting in pregnancies.¹ The time, expense, and personnel necessary for surgical transfer have led to increasing interest in nonsurgical transcervical embryo transfer in recent years. Improvements in technique combined with operator experience have yielded sometimes inconsistent results, with pregnancy rates of 50–75%, approaching those of surgical transfer.2 This paper will report the results of a nonsurgical technique used in a commercial embryo transfer program during the 1998 breeding season.

2. Materials and Methods

Fifty-five mares of various breeds were presented by clients for embryo recovery and transfer. Fifteen of these mares had no history of reproductive problems and were presented simply to produce multiple pregnancies; 10 show mares were presented to produce foals while still showing; and 30 mares were admitted with a history of infertility. All mares were bred via artificial insemination, 5 with fresh semen, and the remainder with transported freshcooled or frozen semen. Embryo-collection flushes were performed 7 days after ovulation with a 30F silicone balloon catheter. The uterus was flushed with three successive liters of Dulbecco’s phosphatebuffered saline (PBS) with 1% fetal calf serum containing 100 U/ml of sodium penicillin and 100 µg/ml of streptomycin sulfate. After initial infusion, each liter was drained from the uterus through a 75-µm embryo-recovery filter.a The uterus was manipulated per rectum to maximize fluid contact with the endometrium and fluid recovery. Larger volumes of PBS (1.5–2 liters per infusion) were utilized in mares that had particularly large uteri. Each mare was administered a luteolytic dose of prostaglandin at the completion of the flushing procedure. […]