Thin body condition of a horse might represent true “weight loss,” or, more likely, it might be secondary to inadequate calorie intake over a period of time. The identification of a thin horse is usually not difficult–the horse’s owner, stable manager, and veterinarian can clearly see that a horse is underweight. For a time, weight loss or poor condition might be hidden by a long winter coat, or under a winter blanket. Determining a horse’s body condition score can be useful in adding a more objective measurement to a subjective finding such as weight loss. Additionally, determination of a horse’s ideal weight depends on the breed of horse and intended use. For example, an event horse is usually in leaner body condition than a show hunter.

There are three main causes of unplanned weight loss: Malnutrition, parasitism, and dental problems.

Malnutrition means the horse isn’t receiving enough calories. This might include inadequate amounts of hay and grain, poor-quality feed, or that there’s competition for feed in a turnout situation. Competition arises when, for example, a bossy Quarter Horse is housed with a high-strung Thoroughbred. Each horse might be fed appropriate amounts of hay and grain for his body weight, but the Quarter Horse might be eating his intended (smaller) meal and chasing the Thoroughbred away from his much-needed meal.

Parasitism might rob the horse of calories through the parasites’ consumption of nutrients or by inflammation associated with parasite burden. Regular (every two to three months) administration of deworming agents in association with routine fecal egg counts should minimize the impact of parasites on the horse’s weight.

Dental problems can limit the horse’s chewing efficiency, making digestion incomplete. The presence of broken, loose, or infected teeth can make chewing so painf