Friesians' Blood Work Alike but Different

“Friesian breed specific reference intervals provide a more accurate means for veterinarians to evaluate and treat Friesian horses under their care,” Fox said.


When it comes down to the blood coursing their veins, a horse is a horse, right? Not necessarily, say researchers who compared Friesians’ complete blood count and chemistry values to general horse population reference intervals for adult horses, revealing that veterinarians caring for the 10,000-12,000 Friesians in North America should interpret a few test results differently than they would in the average adult horse.

Katherine Fox, DVM, head of research at The Fenway Foundation for Friesian Horses, based in Hortonville, Wisc., worked with researchers at the University of Wisconsin’s School of Veterinary Medicine, in Madison, and with IDEXX Laboratories, in Columbus, Ohio, to determine these reference intervals (RI) for Friesians. She presented the group’s results at the 2013 American Association of Equine Practitioners’ Convention, held Dec. 7-11 in Nashville, Tenn.

Fox said that while a lot of research is available on problems commonly referred to as the “Big Four” in Friesians—megaesophagus (chronic dilation of the esophagus), aortic rupture, dwarfism, and hydrocephalus (fluid on the brain)—there hasn’t been information available on basic differences between this breed and other full-sized horse breeds. Recently, Friesian owners contacted The Fenway Foundation, a Friesian-focused organization, with a desire to understand “more subtle concerns” that could be evident on blood work. Few studies exist on breed-specific reference intervals across the equine species.

“Knowledge of how Friesian horses are alike and different (as compared to other breeds), with respect to their blood values, will allow for more accurate diagnosis, treatment, and more reliable response to therapy,” she said.

The research team sent out a questionnaire to Friesian owners in the United States and Canada, and 127 horses met the study criteria. The scientists included both males and females, recognizing there can be differences among them, and they assessed animals from age 3 to 18 (though the vast majority of the animals were 6- to 10-year-olds), since young horses can have different blood values than adults. All horses resided in North America, and they had no disease 30 days prior, the day of, or 30 days following the blood collection.

IDEXX laboratories ran the samples, analyzing them within 24 hours to minimize changes that can occur in vitro (outside the horse’s body). They processed every sample the same way and determined that many of the values, from red blood cells and leukocytes to electrolytes and enzymes, fit well within reference intervals that IDEXX established for the general horse population.

But a few of the values were different. Among them was glucose: Fox said she found that “21 of the horses had a glucose value that was lower than the general horse population. This may have been the result of a longer time between the blood draw and centrifugation of the blood, or it may be the Friesian horse itself.

“In summary, we found 11 hemotologic and 19 biochemical general horse reference interval values that were acceptable for use with adult Friesian horses,” she said. “There were three hemotologic and two biochemical values for which Friesian-specific RI values should be used.” These included hemoglobin, red blood cell count, hematocrit, glucose, and lactate dehydrogenase.

Fox explained that “use of these values will help to prevent overdiagnosis of conditions such as anemia, hypoglycemia, and muscle or liver injury, thus eliminating unnecessary diagnostics and treatment. It will also help to alleviate the confusion that occurs when a Friesian horse fails to respond to therapy.

“Friesian breed specific reference intervals provide a more accurate means for veterinarians to evaluate and treat Friesian horses under their care,” Fox said. “Correct interpretation of the blood results that are seen ‘on paper’ and understanding what is truly happening within that Friesian horse will allow all of us, owners and veterinarians, to move forward with confidence that we are all doing our best to keep these wonderful Friesian horses healthy and happy.”

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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