July 22, 2019 – Endocrine-disrupting chemicals frequently are in the news for the risk they pose to the health of humans and wildlife. As it turns out, our horses may also suffer ill effects and be at an even higher risk of developing a devastating health condition.
Morris Animal Foundation-funded researchers at the University of Minnesota found endocrinedisrupting chemicals (EDCs) in a horse’s environment may play a role in the development of equine metabolic syndrome (EMS). They recently published their findings in the journal Chemosphere.
“This is a pivotal piece of a very complicated jigsaw puzzle. There are a lot of horse owners out there who are very diligent about providing their horses fantastic care, but the horses are still diagnosed,” said Dr. Molly McCue, Professor and Interim Associate Dean of Research, College of Veterinary Medicine, University of Minnesota. “It’s important to be aware that these chemicals contribute to the problem, so we can look for ways to reduce horses’ exposure to them.”
EMS, which has no cure, is caused by endocrine dysfunction, including insulin dysregulation, in horses. They can’t process glucose correctly and frequently become obese. It’s known to be one of the most common causes of laminitis, a painful and debilitating inflammation of tissue in a horse’s hooves, leading to reduced performance and, in severe cases, necessitating euthanasia. What isn’t known is what causes EMS, though inappropriate diet, lack of exercise and/or seasonal changes are contributors.
Recently, researchers noticed horses living close to federal Superfund sites, where EDCs may be concentrated, were more likely to have a history of laminitis and biochemical abnormalities related to EMS. EDCs are chemicals that are almost always man-made substances. Originally, they were pesticides and herbicides, such as the infamous Agent Orange. Today, we also find them in many plastics and personal care items.
EDCs are prevalent in the environment and can mimic a body’s hormones, blocking actual hormones from doing their job. Because of this, they are known to produce harmful effects in humans and wildlife. Horses, researchers suspect, likely come into contact with EDCs through their food.
The Minnesota team followed up on their discovery by studying more than 300 horses from 32 farms in the United States and Canada. They focused on Welsh ponies and Morgan horses, as these breeds are more likely to develop EMS than others. The team collected data on the horses’ lifestyles, including diet, exercise and past illnesses, as well as their farm location.
Researchers also examined the horses’ plasma and looked for EDCs that have effects on cell receptors. At the same time, they determined whether an individual horse had blood test results consistent with an EMS profile (including insulin and glucose at rest and following a sugar challenge). The team then analyzed the results to look for correlations between plasma EDC concentration and these variables.
The team concluded that accumulation of EDCs may explain some environmental variance seen in horses with EMS, but they are still defining the precise role. Dr. McCue said more research is needed to determine how significant the association is, but hopes future studies will improve scientific understanding and advance preventive veterinary care for horses.