OVC Research to Decipher Vitamin D in Horses with Enterocolitis

Could the same biomarkers linking low vitamin D to seriously ill humans be present in horses? Starting this spring, Ontario Veterinary College researcher, Dr. Luis Arroyo and his team will be collecting and analyzing equine blood samples measuring vitamin D and other biomarkers of inflammation and systemic disease. They expect to find major disorders of hormonal pathways, much like in human studies looking at hypovitaminosis D as a marker of disease severity. This knowledge could be pivotal to future studies looking into clinical intervention at the earliest stages.

Equine enterocolitis (diarrhea, colitis) is a major cause of equine deaths worldwide. “It is a black box,” says Arroyo as he recalls a staggering statistic from a recently published paper out of California. The paper stated that in 13 years of studying over 700 enterocolitis cases, the cause of the disease was unknown at least 65% of the time. Colitis can result in loss of hormonal control, metabolic/ electrolyte / fluid imbalances, and organ failure.

Horses are hindgut fermenters and they depend on the microbiota in the gut to break down what they eat and produce energy. Disturbance of this ecology will affect the health of the horse directly. Colitis causes inflammation of the intestine and the horse can end up with diarrhea. When this occurs and there is significant nutrient loss, they can end up becoming very sick.

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Vitamin D is involved in regulation of calcium and phosphorus, bone health, controls the immune system, and reduces inflammation. Currently, there is no information on how the blood levels of vitamin D change in sick and healthy adult horses.

“This research project is not about the pathogenesis of colitis but more on how the horse responds to this disease and how the system is coping with it,” says Arroyo. “Much like taking a car to the mechanic and having them perform tests to see what is wrong; the research is very much in the diagnostic stage to see what is wrong in the digestive system.”

“Can we better understand what is going on in these cases and then better manage them, help them recover faster or even prevent them?” asks Arroyo. “With this knowledge comes the possibility of modulating what is going on in the intestine.”

Arroyo stated that it is quite common to have several cases of colitis admitted to the OVC in a month. The diligence in the research will be collecting samples from each horse, every day for at least four consecutive days. They will analyzing at 6- 8 different metabolites. “We want to understand the progression,” says Arroyo regarding the importance of collecting samples for at least 4 days from the same horses.

“The focus will be to follow horses with colitis but we also want to understand patterns in horses with different conditions as well as healthy horses,” says Arroyo. The research plan includes analyzing serum samples of 40 horses, including a control group.

“We are interested in the talk between the adrenal glands and the brain and how one can stimulate or inhibit the other,” says Arroyo. “If disorders of hormonal pathways are discovered, this knowledge will be useful for future studies. Some of these so-called vitamins, they are actually viewed now as hormones, as they have a function more like a hormone playing important roles in multiple organs. Hormone therapy has shown promise in treating humans. We want to see where there are opportunities to intervene in the early stages for horses with colitis.”

Arroyo is looking forward to collaborating with expert in Equine Endocrinology from The Ohio State University, Dr. Ramiro Toribio on this exciting new research study. New OVC faculty, Dr. Diego Gomez, will also be part of the team in this project kindly funded by Equine Guelph.