What is the most common type of calculi in horses?

The most common type of calculi found in horses is calcium carbonate. This type of urinary calculi is formed primarily from calcium carbonate crystals, which are more prevalent in the equine urinary system due to the horse's diet and metabolic processes. Horses typically consume a diet that is high in calcium, which can contribute to the formation of these calculi. Calcium carbonate stones may cause various urinary issues, including obstruction and discomfort.

In contrast, struvite and calcium oxalate stones are seen in other species more frequently and are less common in equines. Urate stones, derived from uric acid, can occur, particularly in certain conditions, but they are also not as prevalent as calcium carbonate stones in horses. Thus, the predominance of calcium carbonate calculi aligns with the typical urinary composition and dietary influences observed in horses.