An obese horse is often—though not always—an insulin-resistant one, and detection methods for insulin resistance can be tricky to time, not to mention labor-intensive. François R. Bertin, DVM, a resident at the Purdue University College of Veterinary Medicine Teaching Hospital described a new testing technique that he has found useful for identifying insulin-resistant horses at the 2011 American Association of Equine Practitioners convention, held Nov. 18-22 in San Antonio, Texas.

The pancreas’ beta-cells are responsible for secreting insulin to stimulate glucose uptake by glucose receptors. The glucose is moved into muscle cells where it is either used immediately or stored as glycogen for later access. An insulin-resistant (IR) horse has a decreased sensitivity to insulin (as a result, higher amounts of insulin are released than normal in response to ingestion of starch and/or sugar) along with a decreased maximal response to this hormone. High levels of circulating insulin in the bloodstream could put such a horse at risk for development of laminitis.

The recommended insulin-response test requires a veterinarian to take several blood samples over four hours. Bertin described an alternative testing procedure able to produce information on suspect IR cases, especially those horses with equine metabolic syndrome (EMS). While a cresty neck and fat pads at the base of the tail can be signs of EMS and indicative of a probably IR case, he emphasized that a definitive test is necessary for an accurate IR diagnosis.

In a research trial Bertin tested 12 horses around 16 years of age with body condition scores ranging from 3-9 (5 be