Deciphering Vitamin D’s role in horses with diarrhea

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Canadian researchers hope to provide fresh insights into diarrhea and gut inflammation in horses, in particular the role of Vitamin D levels.

The study team will examine whether the same biomarkers that link low vitamin D to seriously ill humans are present in horses.

Starting this northern 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 low levels of vitamin 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 from California. It states that in 13 years of studying more than 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 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.

Vitamin D is involved in the 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,” Arroyo says.

“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 says it is quite common to have several cases of colitis admitted to the Ontario Veterinary College 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 be analyzed for 6 to 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,” Arroyo says. 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,” he says.

“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 says he is looking forward to collaborating with an expert in equine endocrinology from The Ohio State University, Dr Ramiro Toribio, on the study. A new member of the Ontario Veterinary College faculty, Dr Diego Gomez, will also be part of the team.

The project is funded by Equine Guelph.

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