A Method to Obtain Pregnancies in Mares Using Minimal Sperm Numbers

Insemination at the uterotubal junction is a practical technique that can be used to decrease the number of spermatozoa used per insemination. Video endoscopic insemination allows one to visualize the uterotubal papilla during the insemination and provide higher pregnancy rates than a flexible AI catheter. Further studies are needed to determine if a consistent technique can be developed for deposition of sperm on the uterotubal papilla using a flexible catheter. The use of low-dose insemination is important for situations where sperm numbers are lacking, such as subfertile stallions, heavily booked stallions, cryopreserved sperm, and sexed semen. Using video endoscopic insemination, we were able to obtain approximately a 40% pregnancy rate with one-time insemination of 5 million fresh sperm, 5 million frozen/thawed spermatozoa, and 5 million fresh, sexed sperm. Further studies are needed to improve pregnancy rates with sexed, frozen equine sperm. Authors’ address: Animal Reproduction and Biotechnology Laboratory, Colorado State University, Fort Collins, CO 80523 USA. © 2000 AAEP.