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Equine Metabolic Syndrome: More on Horse DietsBy Kentucky Equine Research Staff · August 9, 2016

Obesity among horses certainly has its drawbacks, including decreased exercise tolerance and the development of insulin resistance and laminitis. Researchers now know that simply being obese does not automatically mean a horse has or will develop insulin resistance. So, what exactly does determine whether or not an overweight horse will become insulin resistant?

To answer this question, one group of equine researchers recruited 33 horses (Standardbreds and Andalusians) and ponies, and offered either a cereal-rich supplemental feed (micronized corn) or a fat-rich supplemental feed on top of their regular diet. The amount of supplemental feed was increased over the study period to induce weight gain.

After 20 weeks, horses and ponies offered both supplemental feeds were indeed overweight and considered obese with a body condition score greater than 7 regardless of breed.

Animals in the cereal-rich group had lower sensitivity to insulin and a higher insulin response to glucose than the fat-rich or control groups. In addition, the cereal-rich group also had lower adiponectin concentrations than the fat-rich and control groups. Adiponectin is a protein hormone produced by fat cells that plays a crucial role in controlling fat and glucose levels in the body.

Further, there was a significantly more distinct change in insulin sensitivity in the ponies and Andalusians than in the Standardbreds, illustrating the fact that certain breeds may be more sensitive to cereal-rich types of feed than others.

Interestingly, horses and ponies in the fat-rich group had no difference in insulin regulation than the control group.

This study provides additional evidence that simply gaining weight or being overweight does not induce insulin resistance, which can lead to equine metabolic syndrome. Instead, offering excessive cereal-rich meals appears to be a more important factor. In addition, low levels of adiponectin seem to play a role in insulin dysregulation.

“Although this study shows that cereal-rich meals contribute to insulin resistance, the take-home message is not to stop feeding cereal grains to horses,” advised Kathleen Crandell, Ph.D., an equine nutritionist for Kentucky Equine Research (KER).

Instead, keep in mind that the animals in this study were not being exercised and were gaining weight. “This study reveals the hazard of overfeeding starch-rich meals to horses that do not need the calories for work or sport, particularly horses of certain breeds. Cereal-rich feeds are still appropriate for horses that are performing and need extra calories to maintain weight. Further, a concentrate that provides a balance of energy sources, such as starch, fat, and fiber, is still the ideal feed for the performance horse,” advised Crandell.

*Bamford, N.J., S.J. Potter, C.L. Baskerville, et al. 2016. Effect of increased adiposity on insulin sensitivity and adipokine concentrations in different equine breeds adapted to cereal-rich or fat-rich meals. Veterinary Journal. 214:14-20.