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Fiber is the Key for Colder Weather
by Melyni Worth, PhD, PAS



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As the weather gets colder, our horses need feeding programs geared for warmth.

Horses use energy in their feed as fuel. This fuel enhances movement, augments tissue repair and maintenance, and generates warmth. What kinds of feed are best for keeping horses warm in the cold months? In a nutshell, the answer is fiber! Fiber, as in good hay. Fiber has a double effect on heat generation, as it provides warmth at two stages: during its digestion and again when the products of digestion are metabolized.

What is fiber?

Fiber is the name given to the long chain of sugar molecules that make up the cellulose and hemi-cellulose material found in the cell walls of plants. As grasses (and other plants) grow, the plant uses energy from sunlight to produce simple sugars from water and CO2 in the air; then the sugars are bound together into chains called starches. The starches accumulate and the plant binds them into longer chains called hemi-celluloses. As the plant grows, it joins the hemi-cellulose molecules together and binds them with a special linkage called a Beta-glycan linkage into branching chains called cellulose. This cellulose is used to make the cell walls.


How does fiber produce double warmth?

First, from the bacterial digestion of the cellulose. Cellulose is a source of energy, because the bacteria in the caecum and colons are able to break it down. As the bacteria break down the cellulose and hemi-celluloses, they generate heat as a by-product of fermentation. This heat passes through the GI tract walls and can be a considerable source of warmth for the horse. In the process of breaking down the cell walls, the bacteria produce waste products as well as heat. Some of these waste products are simple short chain fatty acids, or volatile fatty acids (VFAs). These fatty acids are absorbed from the caecum and colons, and pass to the liver where they are used in fat metabolism.

Second, fiber produces warmth from the metabolism of the fat molecules derived from the cellulose. Energy is derived from feed mainly from the oxidation of two nutrients, fats and carbohydrates. The digestion of hay produces sugars from the simple carbs and fat molecules from the cellulose fermentation. The digestion of grain produces mostly sugar and some protein.(Proteins can be degraded and used to provide energy, especially in emergencies, but it is wasteful and sometimes harmful to continually feed too much protein as an energy source). Starches and sugars, the simple carbohydrates, are digested by the horse in the small intestine. There they are broken down to the component sugars, which cross the GI tract wall and go to the liver. Digestion of these sugars will raise the level of glucose in the bloodstream, called blood sugar. High levels of blood sugar can produce problems, especially in horses with Cushing’s disease or Insulin resistance. Fats are the richest source of energy An ounce of fat will yield 2.25 times more energy than an ounce of carbohydrate. Referred to as lipids, or fatty acids, this class of nutrients includes volatile fatty acids from the hindgut. Horses can digest dietary fat because their liver produces bile salts to help with this fat digestion. Up to 10% of the diet can be supplied as fat, especially if the horse has a high energy need, such as in cold weather.

Sources of fiber

While hay is the main source of fiber for most horses, there are other ways to increase the fiber in the diet. Use of high fiber by-products such as sugar beet pulp and soy hulls or citrus pulp can help increase fiber intake. Winter feeding should consist mostly of fiber, preferably in the form of hay, grass hay being the best. The best way to feed hay is in small amounts at regular intervals throughout the day with the bulk offered at night (when the temperatures are lowest). Or allow the horse to self-feed free choice from a rack or round bale. If hay is in short supply or if the horse cannot eat hay, high fiber by-products can be substituted, such as sugar beet pulp or soy hulls.

If hay is really hard to get, substitute clean barley or oat straw to provide the “chew factor.” The straw does not have much caloric value but it will give the horses something to chew. You will then have to provide some extra calories in the form of fat or starches to make up the shortfall.

Addition of fat to the diet can also help supply the calories needed for heat production. High fat sources include Flax seed, Black Oil Sunflower Seeds, Rice bran and various oils. All of these feeds can help the horse maintain energy production; they also can help the coat be better able to repel the wet and snow.