The wrong diet exacerbates equine metabolic syndrome (EMS) but it doesn’t actually cause it.
It’s easy to see where the idea came from. When a horse/pony/donkey has metabolic syndrome it is very important to limit the sugar and starch in the diet. Starch is digested to glucose before being absorbed. The higher the intake, the higher the animal’s insulin levels will go and the higher the laminitis risk.
However, these abnormal elevations don’t happen with every horse, and evidence continues to grow that metabolic syndrome is genetic.
In 2006, Trieber, et. al., published the results of a year-long mixed breed pony herd study following 160 ponies. There were 54 with a previous history of laminitis, and 106 were never laminitic. The diet was pasture for all. There were exaggerated responses to spring pasture in the previously and currently laminitic group only, and this was “consistent with the expected inheritance of a dominant gene or genes with reduced penetrance”.
Genetics as the root cause is entirely consistent with the observation that certain breeds, like Thoroughbreds, Standardbreds, full size Drafts and Warmbloods rarely, if ever, develop EMS unless they also have PPID. On the other hand, ponies, minis, donkeys, Arabians, Morgans and others are at high risk.
A study published in 2016 by Bamford, et. al., attempted to induce EMS by making horses obese using a high-fat diet, or high-fat plus high carbohydrate meal. They succeeded in making them obese, but not making them insulin resistant. In fact, the horses also fed high carbohydrate had better insulin sensitivity than those fed high fat alone. This adaptation to higher simple carbohydrate intake has been reported before in normal horses.
Research work is ongoing to identify the specific genetic components in EMS. The most helpful way to think of reactions to sugar is that it is like a food allergy. The vast majority of people can eat peanuts, but for some it triggers a severe reaction. It’s not that peanuts are inherently dangerous. It’s the individual sensitivity.
It’s actually not all that simple. For example, exercise can protect from elevated insulin reactions even in susceptible horses. The point is though, that sugar and starch are not the villains here. You cannot cause metabolic syndrome by diet. The issue is the individual’s genetics.
For more information to help equines with EMS maintain good health, see www.ecirhorse.org
Dr. Eleanor Kellon is an established authority in the field of equine nutrition for over 30 years, and a founding member and leader of the Equine Cushings and Insulin Resistance (ECIR) group, whose mission is to improve the welfare of horses with metabolic disorders via integration of research and real-life
Started in 1999, the ECIR Group is the largest field-trial database for PPID and EMS in the world and provides the latest research, diagnosis, and treatment information, in addition to dietary recommendations, for horses with these conditions. Even universities do not and cannot compile and follow long term as many in-depth case histories of PPID/EMS horses as the ECIR Group.