A major new scientific review has highlighted the growing concern over heavy metal exposure in horses, warning that low-level contamination from the environment, feed, water and industrial activity could have serious implications for equine health, welfare and performance.
The review, titled Heavy metals in horses: A review of the toxicity, clinical consequences and expected safe tissue concentrations, examined research into seven key heavy metals and trace elements: arsenic, cadmium, lead, chromium, mercury, nickel and zinc.
Researchers concluded that these substances can accumulate within the horse’s body over time, potentially contributing to a wide range of health problems affecting the nervous system, kidneys, liver, digestion, muscles and reproduction.
Particular concern was raised over cadmium and mercury because of their ability to bioaccumulate, meaning they build up within tissues and may increase in concentration through the food chain over time.
The authors explain that heavy metals interfere with normal cellular function by damaging mitochondria, increasing oxidative stress and disrupting antioxidant systems. Even exposure to relatively small amounts over prolonged periods may have long-term consequences.
For horse owners, the review serves as an important reminder that environmental factors can play a significant role in equine health. Potential exposure sources include contaminated soil, industrial pollution, fertilisers, poor-quality water, some feeds, mining activity, vehicle emissions and agricultural waste.
The paper also highlights how horses can act as environmental “bioindicators”, helping researchers monitor pollution within certain regions.
Clinical signs associated with heavy metal exposure can vary widely depending on the metal involved and the level and duration of exposure. Symptoms may include:
- Poor performance
- Weight loss
- Neurological abnormalities
- Colic or gastrointestinal upset
- Kidney or liver dysfunction
- Muscle weakness
- Reproductive problems
- Behavioural changes
One important aspect of the review is the attempt to compile preliminary “normal” reference values for heavy metals within equine blood, serum, hair, liver and kidney tissues. The researchers believe this could eventually help improve diagnosis, environmental monitoring and food safety assessments.
Although severe heavy metal poisoning in horses is considered relatively uncommon, the review suggests that chronic low-level exposure may be under-recognised, particularly in areas with industrial or agricultural contamination.
The authors stress that further research is needed to establish clearer safety thresholds specifically for horses, as current knowledge remains fragmented.
For owners, practical steps may include:
- Regular testing of water supplies where contamination is suspected
- Careful sourcing of forage and feed
- Monitoring grazing near industrial sites, busy roads or mining areas
- Investigating unexplained chronic health or performance issues
- Working with vets when environmental toxicity is a concern
The review ultimately reinforces how closely equine health is linked to environmental health, and why monitoring contaminants in the horse’s surroundings may become increasingly important in the future.
