Obesity is a serious growing problem in horses, with studies estimating anywhere from 20.6 to 41% of horses are substantially overweight. Of course, this condition impacts more than just the size of a horse’s girth. Obesity is also a key component of equine metabolic syndrome (or EMS), which can put horses at risk for a number of related health issues including the most devastating of all, laminitis.

Because scientists have shown that both obese humans and mice have an altered immune response to vaccinations compared to those at healthy weights, researchers wondered if the same was true for horses with EMS. If true, this could leave EMS horses with less protection against potentially fatal diseases.

Sarah Elzinga, MS, a PhD student studying under the direction of Amanda Adams, PhD, at the University of Kentucky Gluck Equine Research Center, in Lexington, shared what she and her team learned when they conducted a study on the topic at the 2016 American College of Veterinary Internal Medicine (ACVIM) Forum, held June 8-11 in Denver, Colorado.

The team hypothesized that EMS horses, like mice and humans, would have a reduced response to an influenza vaccine compared to their non-EMS counterparts.

In their study the team used the ACVIM Consensus Statement’s criteria of an EMS case, including regional adiposity (i.e., fat deposits on the rump or a cresty neck) or general obesity, hyperinsulinemia or insulin resistance (when the body produces insulin but does not use it effectively), and a history of or predisposition to laminitis. The team also confirmed that none of the horses had pituitary pars intermedia dysfunction, a condition that might also impa