If your horse is at risk for intestinal stones or enteroliths (a common cause of obstruction-induced colic in horses), consider replacing an alfalfa-based diet with grass hay, said Diana M. Hassel, DVM, PhD, of Colorado State University.

Hassel and colleagues evaluated two equine diets and water supplies to see their effect on minerals and the pH of the gut. The gastrointestinal tracts of horses with stones tend to be more alkaline and have higher mineral content. Half of the study horses had undergone surgery in the past to remove intestinal stones, and the other half had no history of stones.

“We found that horses fed alfalfa had a higher pH (more alkaline) in their gut than those fed grass hay,” she said.

Another factor in stone formation appears to be stall confinement versus pasture turnout