Prefer a pdf version of this article? Get it here!

It’s common for horse owners to be challenged in their nutritional fight against their horse’s obesity. Keeping a horse in a lean condition often requires dietary restrictions and careful management of what a horse eats. However, how do you handle a situation where your horse doesn’t gain weight despite a veritable buffet available at all times? When you take stock of your thin horse, you see angular contours of the topline punctuated by visible ribs. No matter how much food is offered, this hard keeper doesn’t easily put on poundage. What to do?

What is Thin?

Estimation of a horse’s body condition score (BCS) is determined by the amount of fat covering a horse’s frame. Scores range from 1 (emaciated) to 9 (extreme obesity). An ideal weight is a BCS of 5.

That said, many equine athletes tend toward a leaner BCS of 4, and show horses tend to be fleshier with a BCS of 6 or 7. A horse that fails to gain weight beyond a BCS of 3 or 4 is considered thin.

It should be noted that a senior horse may appear thin based on prominent withers, spine, and hips, yet sufficient flesh still covers the ribs and torso. With age, muscle that was once robust in a horse’s prime tends to atrophy and be less full.

A thin body condition can develop due to a variety of health issues or due to inadequate or imbalanced nutrition. Have your veterinarian perform a thorough veterinary examination of your horse to appropriately assess and identify potential health issues and dietary strategies that may contribute to thin body condition.

Reasons for Failure to Gain

A common reason for a horse’s thin body condition is due to a lack of groceries—either in quantity, nutrient quality, or both.

Consider how well a thin horse manages to access food within a herd of horses. The dynamics of herd competition may preclude a timid horse from accessing feed, only to find it has all been consumed once he makes his way to the feed area after the other horses have moved away.

Another possibility for insufficient groceries is that the horse may not be provided with enough feed to support his work output. In another scenario, the horse may be offered an ample amount of feed quantity, but it is lacking in nutrient quality. For example, some hay is too coarse to chew, contains mold or too many weeds, or is simply unpalatable.

Dental problems are another reason for a thin body condition score. Horses with poor teeth often have trouble chewing enough to sufficiently extract nutrients. Older horses commonly have dental problems, but other ages of horses are not exempt. Young horses may have retained caps on their teeth that prevent comfortable eating and mature horses can develop sharp points that need routine “floating”.

Mouth pain is a common cause for a horse to back off its feed. Additionally, pain felt when food irritates the stomach lining of a horse with gastric ulcers may also depress the appetite.

There are many other reasons for a horse’s failure to gain weight:

• A nervous horse burns more calories than might be expected.

• Generalized pain or osteoarthritis increases a horse’s metabolic rate to burn calories as well as reducing feed intake.

• Metabolic problems can create high-calorie demands in an ill or geriatric horse— not only is the digestive tract less efficient at processing and absorbing nutrients, but energy and protein requirements increase.

• Kidney and liver disease, and advanced Cushing’s disease exert specialized demands on nutrient requirements. It’s important to manage such diets carefully, avoiding high-fat products in liver disease, calcium-rich feed (legumes, beet pulp) or phosphorus-rich bran in kidney disease, and sugar-dense feed for Cushing’s horses.

• Internal parasite infestation steals nutrients that could otherwise be used by the horse. Studies indicate that chronic parasite damage leads to reduced fiber digestion and compromised colon function.

Climate and temperature also place demands on a horse’s metabolism. Cold weather is more exacting on metabolism than warm periods, with reported 30–50 % increases in energy demand in subzero temperatures—use shelter and blanketing to help reduce metabolic demands. Insect season also saps calories due to the constant motion of horses stamping at these pests.

Training, travel, and competition must also be factored into the calculation of energy demands, and lactating mares or breeding stallions also require consideration of their increased energy needs.

Strategies for Weight Gain

To improve a typical horse by one BCS score means that he must gain around 40–45 pounds, usually accomplished over a 2–3-month period. Once health problems have been addressed, what are the best choices to provide concentrated calories?

A horse typically consumes 1 ½–2 ½% of its body weight per day: For example, a 1,100-pound horse eats 16–28 pounds per day. As a general rule to ensure optimal digestive health, at least 60% of the diet should be in the form of forage (hay or pasture).

Food must be weighed rather than estimated by volume to account for the exact amount fed. Every bale and flake of hay varies in its weight, and not all concentrate feeds are equivalent in energy density per unit volume. A small weighing scale is an invaluable tool for fine-tuning a horse’s diet.

A hard-keeping horse should have free-choice access to quality grass hay at all times. Early-cut hay, particularly hay cut later in the growing season, is more highly digestible than hay that has matured in the field with later harvesting. This is because more nutrients are available in leafy hay compared to forage that is full of stems.

Supplementation with alfalfa or other legume hay adds calories but shouldn’t comprise more than half of the total forage ration. Alfalfa pellets or hay cubes are reasonable substitutes for legume hay.

Complete feed pellets are another source of concentrated calories, containing about 25% grain blended with high fiber along with balanced vitamins and minerals, and may be supplemented with fat.

Beet pulp, a fiber supplement high in digestibility and calories, is also useful in putting weight on a horse. Beet pulp pellets should be soaked thoroughly in water prior to feeding.

As much as one pound of dry pellets can be fed per day, soaked for 6–8 hours to volume, mixed with complete feed pellets and fat supplements, and split into two or more feedings. Each additional pound of dry beet pulp is equivalent in fiber and calories to about 1.5 pounds of hay.

High-fat products are another great source of safe calories for weight gain. Fat is 2.25 times more energy dense than an equivalent amount of carbohydrates (grain) or protein.

Fat may be blended into complete feeds or fed separately in the form of vegetable oil (100% fat) or stabilized rice bran (20% fat). Rice bran is highly palatable and easier than oil to handle in cold climates. Protect vegetable oil against rancidity and supplement with oral vitamin E as an antioxidant.

A thin horse benefits from being served the daily ration in small amounts fed 3–4 times per day rather than the whole amount split between only two feedings.

A finicky horse tends to clean up smaller amounts of food than if presented with the entire daily ration in one or two feedings. Horses with dental problems prosper well when fed gruel made from complete feed pellets, beet pulp pellets, and fat soaked into a mash.

In some cases, digestive aids such as prebiotics, probiotics, and yeast are offered to facilitate optimal digestive function. Psyllium serves as both a prebiotic and a means of clearing sand and dirt from the digestive tract to improve nutrient absorption.

It also helps to monitor behavioral problems such as stall vices or crib-biting. A horse that chews or sucks wood (cribbing) may display this behavior in conjunction with gastric ulcers. High-forage and high-fat diets can have a calming effect. Antacid preventive supplements and/or anti-ulcer medication may be indicated following an endoscopic diagnosis of gastric ulcers.

Living arrangements can also have a profound effect on a horse’s psychological comfort. Modify stabling to suit the needs of each horse—those that are nervous at being alone may do better in a group whereas timid horses may thrive better on their own.

It is best to separate a thin horse from the herd at feeding times to allow them sufficient time to consume specialized meals. This can be accomplished by separating a horse into its own paddock with ample food from dusk until dawn; then the horse is returned after breakfast to mingle with the herd for the day.

An alternative is to spread hay piles around the area to prevent dominant horses from interfering with eating by subordinate herd members. When possible, group horses according to age and dietary needs.

The Bottom Line

When feeding your horse for weight gain, make all feed changes gradually, taking 2–3 weeks to slowly work up to target amounts. If scales are not available to obtain an accurate reading of your horse’s weight, use a weight tape at regular intervals to monitor relative gains (or losses) of body condition. Diligent attention to your horse’s diet based on your veterinarian’s advice is key to accomplishing your goals. Your horse’s weight gain takes time to reach a target goal and this requires a good dose of patience on your part