Food intolerance
QIs it possible for horses to be allergic or intolerant to certain feeds? I feed alfalfa to my gelding but I’ve heard some horses don’t respond well to it. He sometimes looks a little tense around the stomach area. Lily Gale, Northumberland
AVery little is known about the pathogenesis of food allergies in horses and the majority of research into the subject has concentrated on human food hypersensitivities. For a food allergy to occur, it implies there’s an immunological reaction to an ingested substance. Not all food allergies are truly allergic in nature and a better term for the condition would be ‘food intolerance’. Ingredients that are reported to cause adverse food reactions in some horses include alfalfa, barley, beet pulp, bran, clover, oats, wheat, feed additives and some feed supplements. Detailed information is still lacking and much of the information and advice about so-called food allergies in the horse is care-based and anecdotal.
Sensitive tummies
Some horses may have sensitive digestive systems and they also tend to be the ones that react to a variety of things other than feed — changes in routine and environment, for example. They may be prone to periods of loose droppings, bouts of colic and episodes of unpredictable behaviour. In these situations it’s usually helpful, and improvements are generally observed, if the horse is fed and managed in the same way as a horse that actually has a food intolerance. Food allergies can sometimes be quite difficult to diagnose, and it can delay the process of putting into place correct management strategies to help eliminate the problem. The starting point is obtaining a good history of the horse and gathering information from the person who is responsible for their day-to-day care, bearing in mind that this may not necessarily be the owner of the horse.
Finding the culprit
The only reliable way to confirm a diagnosis of a food allergy is with an elimination diet. Both intradermal allergen testing and serum testing have shown to be unreliable for identifying food allergies, although useful as a starting point for elimination diets. The ideal elimination diet consists of feeding your horse a single protein and carbohydrate source to which he has had no previous exposure. However, this can be tricky. We would recommend limiting the diet to fresh hay from a different grass to that which he’s fed normally (timothy grass, say) and elimination of any feed and supplements from the diet for a period of time to see if the symptoms improve. The food trial should be continued for between eight and 12 weeks to see maximal improvement, although most cases show progress after four to six weeks. If improvement is seen, your horse can then be challenged with items from his previous diet, with one new item introduced each week. This allows the offending items to be identified and permanently removed from the ration.