Horses develop equine metabolic syndrome (EMS) for a variety of reasons, most notably too many calories, not enough exercise and season. But not all EMS is explainable for all horses due to these causes; some horses develop EMS due to environmental factors despite conscientious horse owner management.
Horses with EMS experience insulin dysregulation, obesity and a high risk of developing laminitis. In humans, metabolic syndrome is associated with endocrine-disrupting chemicals (EDCs).
A study by the University of Minnesota, funded by the Morris Animal Foundation, looked at the levels of EDCs in horse blood that might contribute to the development of EMS [Durward-Akhurst, S.A.; Schultz, N.E.; Norton, E.M.; et al. Associations between endocrine disrupting chemicals and equine metabolic syndrome phenotypes. Chemosphere March 2019, vol. 218; pp. 652-661].
More than 300 horses from 32 farms had their blood sampled for the presence of EDCs. Results of horses demonstrating EDCs in their plasma were compared to those individuals diagnosed with EMS through glucose and insulin concentrations at rest and following an oral sugar challenge.
EDCs are the by-products of pesticides, plastics, detergents, cosmetics and other personal care items. EDCs can be assimilated into plants to then be eaten by horses, or ingested in contaminated water sources. It is possible for EDCs to spread by wind.
The concern with EDCs is that they mimic hormones sufficiently to block natural hormones from exerting their normal actions. For example, EDCs affect estrogen receptors and hydrocarbon receptors.
The study demonstrated the presence of EDCs in equine plasma and an association with EMS. It is possible that EDCs are “associated with clinical disease phenotype components” in horses but more research is needed to better define the effects.