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FALL 2005
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MRLS:
The Mystery
Begins to Unravel

Scientists in the UK College of Agriculture have made great strides in solving the mystery behind Mare Reproductive Loss Syndrome (MRLS), which significantly reduced the foal population in Kentucky in 2001 and 2002.

“We started out with a total unknown and in several years we’ve really, really come a long way with it,” said Karen McDowell, associate professor in Veterinary Science and one of the original scientists called on to investigate MRLS, which wreaked havoc on Kentucky’s equine industry in the spring of 2001.

McDowell is one of a group of scientists that has devoted much time and energy to MRLS. Others involved include Bruce Webb, professor of entomology; Neil Williams and Mike Donahue, professors of veterinary science at the Livestock Disease Diagnostic Center; David Horohov, the William Robert Mills Chair of Equine Infectious Diseases; Willem de Villiers, chief of the UK Department of Digestive Diseases and Nutrition; and Kyle Newman, lab director at Venture Laboratories in Lexington.

eastern tent caterpillar
First, they identified the culprit—the eastern tent caterpillar. Then they discovered that caterpillar hairs could poke holes in the lining of a mare’s intestinal tract. This discovery prompted them to hypothesize that bacteria escape through the holes and eventually end up in the fetus, resulting in infection and ultimately, fetal loss.

“The types of bacteria that kill the fetus, a majority of the time, are actually bacteria that come from the mare,” McDowell said. “They don’t come in with the caterpillar.”

Two of the MRLS team members, Newman and Donahue, are sequencing the bacteria in an effort to pin down strains of the organism. McDowell and Horohov are concentrating on the functions of a mare’s immune system and, in particular, its response to the caterpillars and bacteria.

Soon, Webb, Newman, and de Villiers will begin a series of experiments with pregnant mice to determine if the MRLS bacteria move across the mice placentas and infect the fetuses as they appear to do in horses.

“Currently the only way we have to prevent MRLS is to keep mares and caterpillars separated. Hopefully, as our work with this continues, we’ll have other mechanisms of preventing or treating MRLS,” McDowell said.

For more information, go to
www.uky.edu/Agriculture/
VetScience/mrls/index.htm

mare and foal

 

 


These Scientists
Focus on the Horse

by Terri Darr McLean

Research scientists in the College of Agriculture are making it their life’s work to enhance Kentucky’s signature industry.

Dr. MacLeod and Naoki Miura
James MacLeod and Naoki Miura

Helping Horses Remain Sound

When James N. MacLeod in Veterinary Science is asked about his research on arthritis and other joint diseases in horses, he might mention the genetic tools being developed that could help scientists understand how equine diseases occur and how they can be prevented.

Or, he might talk about research to find new diagnostic techniques and medicines for horses plagued by joint problems.

But one topic MacLeod probably won’t broach is the justification for his work.

“Horses are tangibly embraced here; they’re part of the Kentucky culture,” said MacLeod, who holds the John S. and Elizabeth A. Knight Chair for musculoskeletal sciences. “I don’t have to explain to anybody why being a scientist studying problems in horses is important.”

In a state where horses are the No. 1 agricultural cash crop, few people question the necessity of equine research—especially research aimed at solving one of the industry’s most pressing problems.

“Lameness issues are the No. 1 reason why athletic careers in horses are limited,” said MacLeod.

MacLeod and students in his laboratory are studying arthritis and changes in joint cartilage that appear as a horse matures and starts to exercise. He is overseeing experiments that examine changes in how genes are activated, or “expressed,” in chondrocytes, the cells that make and maintain joint cartilage.

“We try to understand how these cells function normally and how their function changes when joint disease develops and the cartilage starts to fail,” he said.

The long-term goals of MacLeod’s research are to minimize the possibility that horses will develop arthritis and other joint diseases and to help them remain sound. Along the way, he also would like to broaden understanding of how new equine-specific genetic tools being developed can be used to identify genes that are important for soundness and durability.

Joseph Purswell
Joseph L. Purswell

Easing the Stress of Travel
Hitting the road with a horse in tow is part and parcel of the equine industry. Some horses adapt well to travel, especially short trips. Others do not, and many of them develop a common respiratory infection called shipping fever as a result of long trips. They are also more susceptible to diseases such as colic, diarrhea, and laminitis.

The reason? Poor ventilation and high temperatures inside a horse trailer, the noise of the moving vehicle, and an unnatural sense of confinement all contribute to stress. And stress in horses—as in people—can cause changes in their immune system and predispose them to disease.

“Transport stress is not a widely known problem outside of the people who actually deal with animals,” said Joseph L. Purswell '05, Ph.D. in biosystems and agricultural engineering (now an agricultural engineer with the USDA’s Poultry Research Unit at Mississippi State University). Purswell has taken a close look at transport stress. “It’s a little bit of a challenge to make people see that this is a problem.”

One person Purswell did not have to convince was Richard Gates, chair of the Department of Biosystems and Agricultural Engineering. With Gates’ guidance, Purswell and Angela Green '02, '04 initiated a unique, multidisciplinary research project on the subject. (Green, B.S. in ag engineering and M.S. in biosystems and ag engineering, is now a National Science Foundation graduate fellow at Iowa State.)

Purswell assessed ventilation and temperature in a trailer during transport. One set of experiments involved a scale model of a wind tunnel, the first such experiments of their kind. Green’s study remotely measured the horses’ heart rate and body temperature during transport—also groundbreaking work.

One of the most interesting implications of the research came from study of blood chemistry changes during transport.

“It has many times been shown that immune protection is reduced for long trips,” Green said. “However, our trip of only 100 miles documented a progression of immune suppression over the short trip duration.”

Both Purswell and Green characterize their research as a first step in bringing attention to the problems associated with transporting horses.

Laurie Lawrence Laurie Lawrence

Studying Foal, Mare Nutrition
UK’s Laurie Lawrence, professor of animal and food sciences, considers it her job—perhaps even her passion—to help Kentucky’s equine industry produce quality foals.

“Foal production in Central Kentucky, not only for Thoroughbreds but for other breeds as well, is a very important component of the whole industry here,” Lawrence said. “Making sure foals are healthy and can be good performance horses are high priorities.”

For her part, Lawrence focuses on mare and foal nutrition. Two research projects are particularly notable.

One of them looked at selenium supplementation of mares and its effect on their foals. Selenium, a trace mineral found in the soil, is important for muscle maintenance and for strengthening the immune response. It is normally ingested by horses while they forage. However, selenium is deficient in the soil in Kentucky, and supplementation is necessary.

The second study looked at foals during the weaning period.

“We’ve been pretty active in looking at either different dietary practices or different management practices that can minimize the stress that’s associated with weaning,” Lawrence said.

Lawrence’s research has gained notice not only for its scientific discovery but for its approach.

“We are unique in what we do in that we really try to incorporate the practical environment the horses are raised in into our research program,” she said.

Lawrence is also looking more carefully at the mare.

“One of the questions that we would like to answer is whether or not, over the course of many pregnancies, mares are getting adequate nutrition,” she said.

A cornerstone of UK’s equine research, Lawrence said, is “the focus we have on graduate students and in producing equine nutritionists who go back either into academia or into the feed industry.”

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The College is home
to the
Equine Disease Quarterly

which includes articles written by
College faculty and other equine researchers and professionals throughout the world as well as up-to-date information on equine disease outbreaks.

The internationally-read publication is funded by insurance underwriters Lloyd’s of London, brokers, and their Kentucky agents and marked its 50th issue earlier this year.

Editors are Roberta Dwyer and David Powell, Department of Veterinary Science, and Neil Williams, Livestock Disease Diagnostic Center.

To read the Equine Disease Quarterly online, go to
www.uky.edu/Agriculture/VetScience/gluck1.htm

 

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