Don’t Rely on Physical Appearance to Assess Risk of EMS and Laminitis

Visually assessing body condition or fat deposits is not a reliable way of determining risk for equine metabolic syndrome (EMS) and endocrinopathic laminitis. This is an important, yet disappointing, finding because having a simple, noninvasive way of identifying at-risk horses and ponies is far easier than measuring levels of insulin and adiponectin in the bloodstream.

All horses with EMS have high insulin levels (hyperinsulinemia), which is a known risk factor for laminitis. Similarly, low adiponectin, called hypoadiponectinemia, has also been identified as a risk factor for endocrinopathic laminitis. Adiponectin is secreted by fat cells and plays an important role in regulating glucose levels, lipid metabolism, and insulin sensitivity through anti-inflammatory, antifibrotic, and antioxidant effects.

Some studies reported that body condition score (BCS), cresty neck score (CNS), and various other measurements such as height and weight-to-height ratio are correlated with insulin and adiponectin concentrations. However, results to date are variable, which highlighted the need for additional research on this important topic.

To investigate this, data from 734 ponies was retrospectively reviewed.^* This included 655 clinically healthy, client-owned ponies and 79 native breed ponies, of which 48% had a history of laminitis. Total adiponectin, insulin, age, and various morphometric measures, including BCS and CNS, were evaluated. The proportion of ponies with high insulin levels and low adiponectin levels in obese and ideal-weight ponies was compared. In this study, researchers considered ideal weight a BCS of 4 to 5.5.

Contrary to the hypothesis that low adiponectin levels would be observed in obese ponies with a BCS greater than 7 (on a scale from 1 to 9), total adiponectin was higher in obese ponies and a greater proportion of ideal-weight ponies were identified with hypoadiponectinemia.

“Also of note, a greater proportion of obese ponies had normal hormone levels (basal insulin and total adiponectin) than ideal-weight ponies in this study,” explained Catherine Whitehouse, M.S., a Kentucky Equine Research advisor.

Further, no association between CNS and total adiponectin was found. This was also surprising considering that one recently published study found that CNS was a stronger predictor of insulin dysregulation in ponies than BCS.

“This study found that BCS and other morphometric measures of obesity did not reliably predict total adiponectin levels. Morphometric measures, such as BCS and CNS, should not be used as the only measure of a pony’s risk for EMS or endocrinopathic laminitis, as certain at-risk animals may be missed. Additional diagnostic testing is recommended for both lean and overweight horses and ponies to evaluate metabolic health,” Whitehouse emphasized.

While an overweight pony may be considered the poster child for EMS and endocrinopathic laminitis, we now know that lean, athletic animals are also at risk. Some experts recommend measuring insulin levels as part of annual health examinations. This could also include measuring adiponectin levels.

“Maintaining horses and ponies in obese or overweight condition is still an unwise practice, as it takes a toll on their joints and overall quality of life. Key strategies to managing weight include restricting pasture access, providing hay and feed by weight rather than volume, and selecting hay and feed that best fits the calorie needs. Such a diet may include mature grass hay and a low-intake ration balancer or a vitamin and mineral supplement mixed with a small amount of hay pellets. This type of diet provides complete nutrition, while supporting digestive health and behavior through maximizing time spent eating,” Whitehouse said.

^*Barnabé, M.A., J. Elliott, P.A. Harris, and N.J. Menzies-Gow. Relationships between total adiponectin concentrations and obesity in native-breed ponies in England. Equine Veterinary Journal:14013.