Deep Horn Insemination Technique

In his presentation "Deep Horn Insemination" at the Hagyard-Davidson-McGee Bluegrass Equine Reproduction Symposium Oct. 25, John Steiner, DVM, Diplomate ACT, discussed two ways to use minimal numbers of sperm deposited at the tip of the uterine horn to achieve satisfactory pregnancy rates. One method involves the use of a videoendoscope for guidance, while the other utilizes a flexible insemination rod guided rectally to the base of the horn. A third method that has been described is surgical oviductal insemination (termed gamete interfallopian transfer, or GIFT).

Deep horn insemination can be useful for several reasons:

  • To utilize low numbers of sperm cells and semen volume;
  • To make more efficient use of subfertile stallions;
  • To make more efficient use of poor-quality ejaculate;
  • To make more efficient use of frozen semen;
  • To minimize post-breeding endometritis (which is normal in most mares, more severe in older mares, and less severe when less foreign material such as semen is placed in the uterus); and
  • To effectively use sex-sorted sperm (which is only used in small numbers as the sorting process is slow and damaging to many sperm).

"In general, mares are inseminated artificially using 500 million (500x106) progressively motile sperm when using fresh or cooled semen, and 800 million to one billion spermatozoa that have been frozen and thawed," said Steiner. In comparison, he stated that insemination with as little as 5x106 spermatozoa (100 times less than the normal amount) can be successful when the semen is deposited at the utero-tubal junction of the uterine horn ipsilateral to (on the same side as) the ovary with the dominant follicle.

Steiner described using a 130-cm-long videoendoscope (10-13 mm wide) delivered with a 190-cm endoscopic delivery catheter for guidance in one version of this procedure. After the mare and semen are prepared, the endoscope is passed through the cervix, then the cervix is held closed (via the rectum) and air is used to dilate the uterus for visibility. "You can inflate the uterus as you go, or guide the endoscope rectally and inflate it at the end," he explained. "But air is irritating to the uterus, so less is better." The air is expelled following insemination.

The other method involves guiding a 57-cm or 65-cm flexible insemination catheter to the ipsilateral utero-tubal junction solely via the rectum. "While the semen is deposited blindly in the anterior horn of the uterus, this is a more practical method for most practitioners," Steiner said.

Steiner discussed conflicting studies on pregnancy rates using various methods of deep horn insemination, noting that the differences in results were quite likely due to variability in operator (veterinarian) technique. Differences in semen quality used and semen preparation procedures could also account for some variation in results. "There are some conflicting results, but with this method we have gotten pregnancies from some stallions that haven't had one in a year or two," he concluded.

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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