Feeding the fat horse: Achieving better body condition through nutrition
Excess weight may cause or predispose horses to problems like joint pain, laminitis and insulin resistance, or it may indicate an existing metabolic disorder. Nutritional management of the overweight horse is key – and not quite as simple as some may think.
At what weight is a horse overweight?
Assigning a specific weight to define obesity in horses is impossible due to differing bone structure and muscling. Instead, evaluating fat deposition over the horse’s body is a better method to estimate body condition. Body condition scoring (BCS) systems have been developed to apply a numerical score to the horse’s condition based on fat coverage over target areas of the body. While BCS systems are subjective, they do provide a systematic method for evaluating body condition. One of the most widely accepted scoring systems is the 1 to 9 Henneke scale, where 1 is extremely emaciated and 9 is very obese. Horses scoring above a 7 on this scale are considered overweight. For more information specific to body condition scoring, you may visit McCauley's dedicated page.
Why is the horse overweight?
Determining why the horse is overweight can be helpful. Sometimes the answer is as simple as the horse receiving feed when little or no feed is required. Unfortunately, the answer is often much more complicated. Metabolic disorders such as Cushing’s disease, insulin resistance and equine metabolic syndrome (EMS) may predispose the horse to obesity. Some horses carry extra weight simply because they are very efficient at converting dietary energy (calories) to fat.
Nutritional management of obese horses
Feed should be adjusted according to body condition and season. One of the primary keys to achieving desired body condition is to balance the number of calories consumed with the number of calories used. The number of calories used changes with age, climate and activity level. As a result, the calorie consumption will likely need to change throughout the year to maintain a healthy body condition. Warmer weather means less energy is used to maintain body temperature, and as pastures grow lush and calorie-rich, winter feeding quantities need to be decreased to maintain a healthy weight.
If reducing or eliminating feed does not accomplish the desired weight loss, grazing on lush pastures should also be limited. This may be accomplished by splitting time between pasture and stall, using a grazing muzzle or placing the horse in a dry lot and feeding hay.
Pastures are often deficient in many trace minerals. A typical trace mineral salt block will not meet the horse’s mineral requirements. If the amount of feed provided is below the minimum requirement, then supplemental vitamins and minerals will be needed. In such cases, vitamin and mineral supplements should be fed daily rather than fed free-choice.
When feeding hay to overweight horses, choose mature grass hay. The more mature the hay at harvesting, the lower the digestible calories. Sugar and starch concentrations are usually lower as well. Many metabolic disorders require avoidance of sugars and starches, making mature grass hay the best choice for reducing calorie intake.
Horses on a hay-only diet should receive a minimum of approximately 1.5 to 2 percent of their body weight per day. Feeding hay at this rate is essential to maintain normal, healthy gut function and to avoid the development of vices like wood chewing. As always, the hay should be free of dust, mold and other contaminants.
Use a body condition scoring system to evaluate the horse’s fat deposition.
Reducing caloric intake and/or increasing caloric output is crucial to weight reduction.
While calorie restriction is important, the other essential nutrients (e.g., protein, vitamins and minerals) cannot be ignored.
For optimal health, the goal is to achieve and maintain the ideal body condition throughout the year. This may require fine-tuning the diet regularly to adjust for seasonality and other factors, such as changes in activity level.