Equids exposed to high iron levels in water, grass, or hay for a prolonged period can accumulate the mineral in their livers, resulting in chronic iron overload. | Photo: iStock

Until recently, the veterinary industry has viewed iron toxicity in equids mainly as an acute condition—the result of overdosing on iron-containing supplements. However, researchers have found that equids exposed to high iron levels in water, grass, or hay over a prolonged period can accumulate the mineral in their livers, resulting in chronic iron overload.

Dutch researchers took a closer look at chronic iron overload after two genetically unrelated horses from one farm in the Netherlands were diagnosed with hemochromatosis (a buildup of excess iron in the body) and liver dysfunction. In all, the team examined 22 cases (21 unrelated horses and a donkey from eight farms) with evidence of hemochromatosis in blood or liver tissue samples. The equids displayed clinical signs of jaundice, weight loss, rough hair coat, and dullness.

The researchers tested water samples from the farms, all of which had high iron levels ranging from 0.74 to 72.5 mg Fe/L—above the maximum acceptable limit of 0.3 mg Fe/L—and were deemed unsuitable as drinking water for animals, they said