Horses generally digest food and absorb nutrients efficiently—but not all the time. Some have trouble maintaining an appropriate body condition score. These are known as “hard keepers.”
Other horses may need to gain weight after an illness or after being acquired from an environment that didn't supply adequate nutrition. Here, learn how to recognize a skinny horse, understand reasons horses may have a lower body condition, and stock the best foods for rapid but safe weight gain.
How To Assess Need for Weight Gain
The Body Condition Score (BCS) is an important and objective scoring system that determines if your horse has adequate fat and muscling condition. As horses lose weight, they will first use carbohydrate reserves (glycogen), which are quickly depleted. Fat stores are mobilized next, followed by the breakdown of muscle into protein. Most BCS scoring is done on a nine-point scale. There are some differences between breed and discipline regarding ideal body condition, but generally a score of 4-5 is ideal. These horses will have symmetric muscling; a slight outline of the ribs may be seen but isn't easily discernible; and there will be a small fat pad over the tail. The neck and withers blend seamlessly together.
It is extremely dangerous to try and rapidly increase body weight in an emaciated horse (BCS of 1-2.5). Likewise, very obese horses (BCS 8-9) are also prone to significant health problems if rapid weight loss is attempted. Neither should be attempted without close veterinary supervision.
Health Reasons for Poor Body Condition in a Horse
The first thing to do in assessing skinny horses is to recognize health issues that may cause them to become inappetent. Healthy horses should be bright and alert, interested in food, and have shiny coats of appropriate length for the season. No nasal discharge should be seen. Their manure should be soft-formed fecal balls. When eating, horses should be able to easily draw food into their mouths using their lips, chew without dropping feed, and swallow normally without coughing.
Your veterinarian should assess horses who become too skinny. Dental issues are a major cause of weight loss in horses. Horses' teeth continually grow and change shape throughout their lives and are ground down by the chewing of roughage (hay and grass). Sometimes the teeth are unevenly ground down, resulting in points that can cut into gums or cheeks and make chewing painful. Older horses grind their teeth down to a smooth surface and may even lose teeth. An oral exam should be performed annually to rule out dental disease even in horses of appropriate weight.
A fecal sample should be taken during the exam to assess for nutrient-stealing internal parasites. Blood may be drawn to check for underlying infections, liver and kidney enzymes, and other diseases. A veterinarian will also ask what you're feeding your horse and whether there's competition between horses in the herd at the feed trough.
A very common reason for recent weight loss in horses is increased energy expenditure. Mares will lose weight after foaling because producing milk requires significant energy. An increase in exercise often requires an increase in caloric intake, too. Another common reason for an increased need for energy is the rapid fall in environmental temperatures. Horses often maintain a body condition just on hay or pasture but grain supplementation is often necessary when winter temperatures drop below freezing. Make sure to check your horse’s body condition daily with their blanket off in cold temperatures, as this change can happen in a week.
Best Foods for Weight Gain
Hay is the largest component of a horse’s diet, and quality varies significantly. Horses should eat between 1.5-2% of their body weight in quality hay daily if pasture isn’t readily available. Often horses need supplementation of hay in winter even if on ample pasture in a seasonal climate. Alfalfa is more calorie-dense than grass hay, which is more calorie-dense than straw.
Rapid weight gain can be tricky to achieve in a horse, as the microbes that live in a horse’s gastrointestinal tract are very sensitive to change. However, some fibers, concentrates, and grains are superior to others in encouraging safe weight gain. Beet pulp is an excellent source of fiber that also promotes safe increases in body condition. It should be soaked before feeding.
Concentrates higher in fat and protein will also promote weight gain more safely than grains high in sugar, as the latter cause rapid shifts in gut microbial population and may lead to colic. Oils (corn, canola, flax, and commercial equine-specific formulas) provide a dense calories in the form of fat without starch. They are especially useful in starch-sensitive horses, such as those with gastrointestinal disease or previous laminitis. Any addition of grain or oil should be made slowly over a period of one or two weeks to give the horse’s gut time to adjust.
All in all, fattening up a skinny horse first requires a bit of detective work for you and your veterinarian. Rule out health problems such as dental issues, high parasite loads, systemic illness, and environmental factors such as herd competition first. Then, assess roughage quality and add concentrates and oils slowly, with emphasis on fiber, protein, and fat above sugars and easily digestible starches.
National Research Council. 2007. Nutrient Requirements of Horses: Sixth Revised Edition. Washington, DC: The National Academies Press.