As breeding stallions age, their reproductive abilities can wane, leaving their breeding managers with a problem--too many mares to breed, and not enough sperm. J. Scott Weems, DVM, of Weems & Stephens Equine Hospital in Aubrey, Texas, has successfully incorporated low-dose hysteroscopic insemination (LDHI)--direct placement of sperm at the site of the oviductal papilla (an ideal site for fertilization) via use of an endoscope and catheter--and he presented information gained from its use during past two breeding seasons at the 2004 AAEP Convention, held Dec. 3-8 in Denver, Colo.

In early 2003, Weems was faced with a problem: A client's 24-year-old Quarter Horse stallion had limited daily sperm output, a demanding mare book, and some very concerned syndicate owners. "They were missing many cycles, creating a large backlog, and had a looming PR disaster on their hands," he said. He was able to incorporate LDHI into an existing artificial insemination (AI) program to inseminate all mares each breeding day without decreasing the number of mares in the stallion book, sacrificing pregnancy rate, or reducing the number of pregnancies produced.

Weems said that 136 mares were to be bred to this stallion during the 2003 season. Mares for breeding were selected by estrus and were examined by rectal ultrasound in order to find softening ovarian follicles. The mares were bred by either standard AI or LDHI, based on the amount of mares presented that day and the available semen.

What made the challenge even more difficult was that "approximately 10% of this horse's book was 20-year-old and older barren mares. There were a lot of performance horse mares too (that must be kept on a training schedule)."

Weems prepares the endoscope by cold sterilization in glutaraldehyde for five minutes for each procedure, and he rinses it with sterile water. He gets the scope gas-cleaned once per week to decrease chances of causing endometritis. "We have done as many as 10 in an hour without much trouble at all," he said.

Performing LDHI is a two-person job. The uterus is slightly inflated as the endoscope is sent past the uterine bifurcation, up through the uterine horn, and to the distal portion of the uterus. The veterinarian can become easily disoriented if the person holding the endoscope doesn't keep their thumb on top (and thus the left-right, up-down orientation clear). "Some papillae are quite obvious, while others are just visible by color," he explained. "Slowly put the semen on the papilla, after which the scope is withdrawn into the uterine body. Passively deflate the uterus."

The overall per-cycle conception rate in these mares increased in 2003 and 2004. In mares bred at least once during an estrus cycle by LDHI, a 47% (176/376) pregnancy rate per cycle was achieved during 2003 and 2004 (compared to 42%, or 121/288 in 2002, when only standard AI was used).

In mares bred with LDHI to carry foals to term, a 57% (55/96, compared to 44.5% or 53/199 in 2002, when only standard AI was used) pregnancy rate per cycle was obtained in 2003/2004. Additionally, a 46% (127/277) embryo recovery rate was obtained in mares bred on donor cycles by LDHI compared to 37% 63/170 in 2002).

Doses as low as 50 million sperm cells were used without affecting conception rates, he said. With such a low dose, however, he needed to make sure that 100% of the sample got out of the catheter and into the mare. "I prefer a large-bore catheter. Becoming quicker while using minimal insufflation (air inflation of the uterus) has helped us eliminate (wasted semen). I deliberately, but aggressively, deposit semen on or near the papillae" with good results.

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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