If your broodmare or stallion is having reproductive problems, you might need a specialist to figure out what's wrong. And that specialist might use knowledge gained from the annual conference of the Society for Theriogenology held in Columbus, Ohio, Sept. 16-20. Theriogenology is described as that branch of veterinary medicine dealing with reproduction, including the physiology and pathology of male and female reproductive systems and the clinical practice of veterinary obstetrics, gynecology, semenology, and andrology.

The topics covered in the equine sector ranged widely--from the practical use of ultrasonography to a discussion of the current status of mare reproductive loss syndrome (MRLS).


W. Thomas Riddle, DVM, and Michelle LeBlanc, DVM, Dipl. ACT, of Rood and Riddle Equine Hospital in Lexington, Ky., authored a paper titled "Update on Mare Reproductive Loss Syndrome." Riddle presented the paper and had this to say:

"In spring of 2001 and 2002, Central Kentucky experienced large numbers of early- and late-term fetal losses in mares of multiple breeds. In addition to the reproductive losses, a number of pericarditis (inflammation of the fibrous sac that surrounds the heart and the roots of the great vessels) and endophthalmitis (inflammation of the eye cavities) cases were identified in Central Kentucky horses during this same time period. Together, these reproductive and non-reproductive cases have been termed mare reproductive loss syndrome (MRLS). Other areas of Kentucky and neighboring states also reported smaller numbers of cases consistent with MRLS."

Riddle then went on to outline the devastating economic impact MRLS had on the equine industry in areas where it struck:

"The economic impact to Kentucky from the 2001 losses was estimated to be nearly $336 million, according to a study conducted by the University of Louisville. In 2001, there were approximately 550 late-term losses, between 2,000 and 3,000 early fetal losses, approximately 30 endophthalmitis cases, and between 50 and 60 pericarditis cases.

"In 2002, fewer cases were seen, with 265 late-term losses, approximately 500 early fetal losses, six endophthalmitis cases, and nine pericarditis cases being reported.

"The economic impact from MRLS will be felt for years following the actual cases. In 2002, the Keeneland November breeding sale was the smallest since 1993, with 864 foals entered, compared to 1,063 in 2001 and 1,379 in 2000. The 2003 Keeneland July select yearling sale was cancelled, with a primary reason being fewer yearlings available as a result of MRLS losses."

Riddle described the treatment approaches taken with at-risk mares at Rood and Riddle Equine Hospital, but concluded that: "In hindsight, these treatments did not appear to be of any help."

Research, Riddle told the group, points a finger at the Eastern tent caterpillar (ETC) as the cause of the outbreak. With that belief in mind, he said, efforts for prevention in 2002 were focused on limiting pasture turnout and reducing or eliminating exposure to the ETC.

Riddle also noted that in experiments, freezing didn't destroy whatever links the ETC to MRLS, but that autoclaving (a procedure that involves sterilizing with high-pressure steam) did prevent the caterpillars from causing abortion experimentally.

Other Topics

Presenting a strong case for the use of ultrasonography by veterinarians in the field was Karen Wolfsdorf, DVM, Dipl. ACT, of Hagyard-Davidson-McGee Veterinary Hospital in Lexington, Ky.

In the past ultrasonography was pretty much limited to universities and referral clinics because the purchase price, in many cases, put it out of reach of the average veterinarian. She said that has changed with technology and competitive pricing.

Today, the affordable equipment is a valuable tool with which a veterinarian can become more skilled if it is used regularly, she said. While ultrasound is valuable when dealing with reproduction problems, it can be used for much more.

Other topics covered, along with their presenters, included:

  • Fetal Sex Determination in the Mare Between 55 and 150 Days, by Richard D. Holder, DVM, of Hagyard-Davidson-McGee. Holder said there are two specific windows of opportunity to identify the sex of the fetus with ultrasonography--between 55 and 90 days of gestation and between 90 and 155 days. The early gestation technique involves finding the genital tubercle (the precursor of the penis in the male and the clitoris in the female) and determining its location relative to other fetal structures. The technique performed between 90 and 150 days, he said, involves finding the external genitalia of the fetus--penis, glans penis, prepuce, and gonads in the male, and mammary glands, teats, and clitoris in the female. At this later stage of gestation, the veterinarian should be able to determine sex 90% of the time on one examination with 99% accuracy.
  • Embryo Transfer as an Integral Part of Today's Equine Practice was presented by David Hartman, DVM, a partner in Performance Equine Associates of Whitesboro, Texas. Hartman told his listeners that embryo transfer (ET) is a rapidly expanding field. He described the procedure and the costs involved and ended with what he termed some disturbing trends: "With the increase in demand for ET, we are seeing a lot of farms and individuals pursuing financial gain in the ET business. This becomes a problem when costs are cut to the point of interfering with proper technique. There also are more non-veterinarians entering the market and offering ET services at low fees. "One final thought," Hartman continued, "as we see different breed associations approve the registry of multiple embryos, we need to be cautious of doing 'too much' to certain donor mares. Some of the greatest mares may well be ruined reproductively at a relatively young age if we are not careful."
  • So Many Mares, So Little (Normal) Semen was presented by Brian S. Carroll, DVM, from Oklahoma City Equine Clinic. "There can be fertility problems when a large number of mares is booked to a single stallion," Carrol said. He outlined an approach for a large breeding farm in an effort to increase the pregnancy rate. One of the key factors involved palpating the mares on a daily basis, rather than every other day. By so doing, they were better able to identify the mares which would ovulate within 24 hours of breeding, which conceived 62% of the time compared to 44% conception for those ovulating between 24 and 48 hours of breeding.

More on Reproduction

A number of abstracts also were presented, including:

  • Relationship Between Testicular Blood Flow, Sperm Output, and Sperm Quality in Stallions, by Heinrich Bollwein of the University of Munich. The study revealed that among fertile stallions, there is a high individual variation in testicular blood perfusion (blood supply within the testes).
  • Fertility Trials with Frozen-Thawed Jack Semen was presented by Rebecca J. Jepsen, DVM, of Iowa State University. Her findings support the theory of cholesterol and glycerol interfering with post-thaw fertility of jack semen.

The next annual gathering of the Society for Theroigenology will be Aug. 4-8, 2004, in Lexington, Ky.

About the Author

Les Sellnow

Les Sellnow is a free-lance writer based near Riverton, Wyo. He specializes in articles on equine research, and operates a ranch where he raises horses and livestock. He has authored several fiction and non-fiction books, including Understanding Equine Lameness and Understanding The Young Horse, published by Eclipse Press and available at www.exclusivelyequine.com or by calling 800/582-5604.

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