Are horses susceptible to meterological manipulation? Not exactly, but two research groups reported their findings of the impact of seasonal variations on horses: one on laminitic ponies and the other on diagnostic test results for pituitary gland dysfunction in adult horses. They presented these reports at the American College of Veterinary Internal Medicine (ACVIM) Forum, held June 4-7 in San Antonio, Texas.

In the research abstract, "Seasonal change in energy metabolism of ponies coincide with changes in pasture carbodyhdrates: implications for laminitis" Kibby Treiber, PhD, and colleagues from Virginia Tech evaluated potential seasonal interactions with laminitis in grazing ponies by measuring pasture carbohydrates and various metabolic parameters in pastured ponies.

Nine of the 30 ponies developed laminitis during the study. Compared to non-laminitic ponies, the researchers observed significantly higher insulin and triglyceride levels in the laminitic ponies. In addition, all ponies had the highest glucose and insulin levels in the spring whereas triglyceride and non-esterified fatty acids (two types of fats) were lowest at this time of year.

"Normal ponies may 'crossover' metabolically and switch from using fat as an energy source in the winter to the carbohydrates found in spring pasture. Ponies at an increased risk for laminitis and insulin resistance may be less able to 'crossover' and therefore cannot cope with carbohydrate levels in spring pasture," explained Treiber. "This can result in the development of laminitis in insulin resistant ponies."

Treiber continued, "Pasture is dynamic and so are animals. We need to better understand how metabolism/physiology interacts with the environment in order to understand how our management can impact health."

Meanwhile, Alabama researchers evaluated the potential impact of seasonal variations on various tests clinically used to diagnose dysfunction of the pars intermedia of the pituitary gland in horses. The results were presented by Christopher Schreiber from Auburn University's College of Veterinary Medicine in Alabama in the presentation, "Seasonal variation in diagnostic tests for pituitary pars intermedia dysfunction in normal aged geldings."

While significant differences in α-melanocyte-stimulating hormone were identified based on season, the overall seasonal effect on tests for pituitary pars intermedia dysfunction were less obvious in Alabama compared to horses residing in the northeastern United States.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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