Sulfur in Drinking Water for Horses

In some areas of America, water from springs and wells has a discernible rotten-egg smell that indicates the water contains a high level of sulfur. Horse owners may wonder whether drinking this mineral-laden water will impact the health of their horses, either in the short term by causing colic or laminitis, or in the longer term by triggering skeletal problems in foals.

While there are some nutritional mineral imbalances that can cause serious problems for horses, sulfur is generally not a culprit, according to Kentucky Equine Research equine nutritionist Kathleen Crandell, Ph.D. “Other livestock are rather intolerant of high sulfur, but the horse has always been found to be very tolerant,” she explained. “I don’t know of any reports of sulfur toxicity, likely because the horse has an efficient way of ridding the body of excess sulfur. This mechanism does involve calcium; the sulfur binds to calcium and then is excreted in the urine. However, I have never seen any link to developmental orthopedic disease.”

High sulfur intake can sometimes predispose a horse to uroliths, especially if there is excess calcium in the diet, Crandell said. Uroliths—rock-like mineral masses that can form in the horse’s bladder and possibly obstruct the flow of urine—are uncommon in horses. Small uroliths may be passed naturally, though larger ones may need to be removed surgically.

While it is unlikely that ingesting sulfur in drinking water will harm most horses, owners who are concerned about the water available to their horses can have it tested to find the mineral levels it contains. Some substances found in ground water are potentially dangerous to horses, and an equine nutritionist can advise owners as to whether they need to use a different water source for the equines in their care.