Artificial Insemination: It's Not How Much You Have, It's Where You Put It

When it comes to artificial insemination in horses, the site of deposition might have a big impact on the procedure's outcome. Placing semen directly into the uterine horn containing the ready follicle could allow breeders to use far less ejaculate per mare, maximizing stallion fertility rates, and reducing the likelihood of endometritis, according to Juan Samper, DVM, PhD, Dipl. ACT, of Langley, British Columbia, Canada, who presented his findings on the subject at the Florida Association of Equine Practitioners (FAEP) Promoting Excellence Symposium, held Sept. 27-29, 2007, at the Atlantis resort on Paradise Island, the Bahamas.

Normally, a veterinarian will place the semen in the uterine body. The sperm will travel, in near equal numbers, into each uterine horn. But only one horn actually contains a follicle--so half of the sperm are wasted, in effect.

"That tells you that we can probably reduce the number of sperm cells needed to reach that site where the follicle was," Samper said.

Reducing the number of sperm cells required per dose could:

  • increase the number of mares that could be bred per ejaculate;
  • maximize the effectiveness of sperm per dose (which is especially important in the case of a limited supply of semen, such as with stallions that have died, have been gelded, or have fertility problems);
  • increase the efficiency of sex-sorted sperm (since sex-sorted doses contain less sperm due to the removal of sperm that bears genetics for the undesired sex);
  • allow breeders to better utilize stallions with suboptimal ejaculate; and
  • reduce the likelihood of endometritis (inflammation of the innermost lining of the uterus) by reducing the amount of sperm--which can contribute to this inflammation--in the uterine environment.

Samper performs deep-horn artificial insemination by using a small-diameter flexible pipette guided via rectal ultrasound. He guides the pipette as close to the uterotubal junction (where the ovarian follicle is present) as possible before depositing the semen.

These methods require about half the amount of frozen ejaculate as traditional artificial insemination.
He said this method is inexpensive, requires limited equipment, and quick once the veterinarian has some experience. The hygiene requirements are identical to those employed for the traditional approach to artificial insemination.

In one study of deep-horn insemination, the researchers used 25 to 300 million sperm. Of the mares in the study, 73% became pregnant, with no correlation to the volume of ejaculate used.

In another method, the veterinarian inflates the uterine horn with air, then uses a videoendoscope to deposit the semen in the path of the follicle.

"It looks like there's a pretty consistent, but not a very high difference in the pregnancy rate between rectally-guided and endoscopic insemination," Samper said, noting that there's about a 4% difference in pregnancy rate when the semen is deposited via endoscope versus the rectally guided technique.

These methods require about half the amount of frozen ejaculate as traditional artificial insemination.

As for reducing endometritis, Samper said reducing the number of sperm introduced into the uterus has a big impact on the uterine environment and its ability to maintain a pregnancy.

"We know that one the things that causes the inflammation in the mare is the number of sperm--it's not the fluid or the extender, but the number of sperm cells," Samper said. "It does seem like there is a reduction in the number of white blood cells (indicative of fighting infection) in the uterus when you reduce the number of sperm cells."

Wrapping up, Samper said these methods can help a veterinarian and a breeding operation to make a little semen go a long way, without increasing the risk of inflammation in the delicate uterine environment.

"I think this is something we're going to be asked to do," Samper said. "Mare owners are going to be requesting these techniques."

About the Author

Erin Ryder

Erin Ryder is a former news editor of The Horse: Your Guide To Equine Health Care. She owns a portly gray gelding named Duncan and dabbles in several equestrian disciplines, with an emphasis on dressage.

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