Search for Chronic Disease Risk Factors In Horses Lead to Clues About Prevention
Submitted by: Donna McDonald
Phone: 540-687-3521 ext 22
Email Address: dmcdo05(at)vt.edu
Date Added: 2/4/2008
Article appeared in Innovations, 2008 a publication through Virginia Tech College of Agriculture and Life Sciences.
Search for Chronic Disease Risk Factors in
Horses Leads to Clues about Prevention
By Lori Greiner
It’s not just humans who need to be concerned with their eating habits and waist sizes these days. Researchers at Virginia Tech are finding that obesity and other risk factors may play an important role in the development of chronic health conditions in ponies and
horses, including pasture-associated laminitis, a painful and debilitating condition of the foot.
Faculty members and students at the Middleburg Agricultural Research and Extension (MARE) Center have begun to take a closer look at a naturally occurring model of metabolic syndrome. Kibby Treiber, a recent Ph.D. graduate in animal and poultry sciences, discovered a set of risk factors associated with the increased risk of pastureassociated laminitis in a group of ponies, with obesity and insulin resistance as the primary criteria. The factors include obesity with regional fat deposits, especially over the crest of the neck “cresty neck”, and blood parameters that relate to
insulin resistance and high circulating triglycerides.
“The identified risk factors were associated with an 11-fold higher risk for developing an episode of pasture laminitis,” says Ray Geor, Paul Mellon Distinguished Professor of Agriculture and director of research at the MARE Center.
These factors are similar in principle to those that are applied to the human metabolic syndrome, which include unhealthy cholesterol levels, high blood pressure, high blood sugar, and excess belly fat. They tend to increase the odds of serious health problems such as heart disease and diabetes. “The overall corollary with the human metabolic syndrome is very strong,” says Geor.
Geor and his colleagues are also looking at how pasture changes over the seasons, particularly in terms of its carbohydrate content, and how it affects the horses’ metabolism. They have expanded the study to follow a group of Thoroughbred mares over a 12-month cycle to see how their metabolism changes and how these changes relate to the risk for disease.
They have found that in the springtime when the pasture conditions are very conducive to rapid grass growth, the pasture that is green and lush has a very high carbohydrate content, resulting in very high circulating insulin concentrations in the mares.
According to Geor, when insulin reaches a high point, at least in some animals, it increases the risk for an episode of laminitis. This change in risk can occur very quickly, as shown in more recent studies in the ponies under observation. “Unfortunately for
the ponies, that very scenario developed where there was a little bit of rain and the conditions were warm enough for the grass to change. The insulin concentrations in the ponies shot up, and in one week there were eight cases of laminitis,” says Geor.
“These changes have important implications to understanding what is really the fundamental cause of the laminitis condition,” he says. “And also on how we can strategize to help ponies and
horses to avoid the disease.”
Diet and body type are not the only factors associated with laminitis. Geor points out that certain breeds of ponies and horses, such as Morgan, Paso Fino, Saddlebred, and Arabian, tend to be more susceptible than others. However, he is careful to point out that there are probably sectors within breeds where there is likely to be a difference in susceptibility.
The aging process may also be a factor. A Thoroughbred typically would not be in the high-susceptibility category; however, Geor has noticed that as their mares age, they tend to take on more of the easy keeper appearance as compared to when they are younger. There seems to be an age factor in ponies as well. “We don’t tend to see a problem when the ponies are less than three or four years of age,” he says.
According to Geor, genetics does play a role in the laminitis puzzle. “It’s likely that in the case of laminitis, more than one gene contributes to the disease,” he says. “It is probably not going to be straightforward, but perhaps we can identify a few genes that are key as far as susceptibility and maybe there could be a blood or hair test that could be applied to help an owner better understand the risk.”
Preliminary research has been completed on the genetic aspect of the disease, and the MARE Center is collaborating with other universities to expand this area of research. Geor points out that the introduction of the horse genome could provide additional tools to tackle the genetic question.
Identifying the metabolic syndrome’s cluster of risk factors and understanding how pasture conditions affect the likelihood of inducing laminitis in susceptible animals brings Geor and his colleagues closer to developing strategies for prevention. “We are all about prevention,” says Geor. “If we can do things that prevent the disease from developing, that is the ultimate goal.”
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