Bottom Line
The effectiveness and correct dosing for digestive enzymes in horses is unknown. We'd avoid using them in a healthy horse. If your horse has digestive or weight problems, explore other options first to determine the cause.
If you try digestive enzymes, stick with products that focus on protein- and cellulose-digesting enzymes and stay within the suggested dosages. Don't waste your money on products that contain high lipase. These are more appropriate for a human or pet because their diets are much higher in fat than a horse's. Amylase is only likely to help if the horse is getting grain. Protein-digesting enzymes and cellulose/xylanase are the primary ingredients likely to help a horse. Look for higher levels of these than amylase or lipase.
Overdoses can cause stomach irritation and even ulcerations in the intestines, and this is particularly a concern since we don't know safe or optimal dosages for equine digestive tracts. Stick to manufacturers' recommendations for use in horses, and be alert for any worsening of symptoms or new intestinal symptoms. If these occur, stop feeding the enzymes immediately and let the product manufacturer know.
If you don't see an obvious improvement after a month, stop using the product and talk with your vet.
