Energy-Producing Nutrients for Horses

How the horse’s body uses nutrients to produce energy can be a very complicated concept. But an understanding of this concept is important for proper feeding management and maintaining horses in good body condition.

For equines, the two basic energy-producing nutrients are:

carbohydrates;
fats (also known as “lipids”).

Carbohydrates and fats are very efficient at producing energy. Protein can and does supply energy, but much less efficiently than carbohydrates and fat.

Energy Requirements from Nutrients

Horses’ energy requirements vary greatly, depending upon many different factors. That means their energy requirements from nutrients will vary. Among these factors that can influence energy needs from nutrients are:

maintenance needs;
work or exercise (type, speed, duration);
the animal’s condition;
the amount of weight the animal is carrying or pulling;
terrain over which the animal works or exercises—hills, flat ground, rough, etc.;
growth;
reproduction status;
lactation (milk production) environmental temperature and humidity;
and more.

In addition, as with any other living thing, metabolism rates vary greatly from one individual to another. For these reasons, establishing energy requirements for a particular horse has always been a difficult task.

Too Much or Too Little Energy from Nutrients

Yet the task of establishing energy requirements is necessary—because a diet that fails to provide adequate amounts can cause:

slowed growth rate in young animals;
a decrease in body weight;
unthrifty condition;
fatigue in working or exercising animals;
reduced milk production.

A diet that provides too much energy can also cause problems, including obesity, colic, founder, poor reproductive function (in some excessively fat mares and stallions), and a decreased life span.

In order to understand energy, one must understand some simple chemistry principles. These are discussed in the below sections on carbohydrates and fats.

Carbohydrates

Carbohydrates are chemical compounds contained in all plants and in the grains produced by plants. Carbs are the major energy source for horses, supplying much of the fuel needed to run the body’s functions.

Carbohydrates are made up of carbon atoms. They also include hydrogen and oxygen atoms. Compounds that are considered carbohydrates include:

sugar;
simple sugars known as “monosaccharides”
complex sugars known as “polysaccharides”
starch;
fiber; and
other related compounds.

Carb Categories

When talking about digestion in the horse, carbohydrates are divided into two main categories:

Non-fiber carbohydrates: These are also referred to as nitrogen-free extracts, or NFE. These are the carbohydrates that are more easily broken down and more readily absorbed by the horse’s digestive tract (and so are also referred to as the “soluble carbohydrates”). They are mainly made up of starch and sugar molecules that are broken down in the stomach and small intestine. This occurs before they get to the large intestine and is referred to as pre-cecal digestion (meaning “before the cecum”). The enzymes present in the horse’s digestive tract can easily break down most of the non-fibrous carbohydrates or nitrogen-free extracts.

Fiber: The carbohydrate portion of plants and grains includes cellulose, hemicellulose, and lignin. These carbohydrate compounds are mainly broken down by bacterial (microbe) action in the hind gut, beginning in the cecum and continuing through the rest of the large intestine. This is referred to as post-cecal digestion, meaning “in or after the cecum.” It is also referred to as “hind-gut fermentation.”

Equids are designed to eat mostly forages (both pasture and hays) and to have a high amount of fiber in their diets. Be careful not to feed your horse too much grain (concentrate). An interesting fact about fiber and equines: Research has shown that donkeys are more efficient in digesting fiber than are horses and ponies. Thus, donkeys can be fed higher-fiber diets than some other equine species.

Both nitrogen-free extracts (the non-fiber carbohydrates) and fiber release energy when broken down in the digestive tract of the horse. Energy not needed by the body at the time of digestion is stored in the form of glycogen—which is an end product of the digestion of starches, sugars, and fiber. Glycogen is stored in the kidney, liver, and muscles.

If at any time the glycogen storage capacity of the kidneys, liver, and muscles is full, the body stores the excess simple sugars or “monosaccharides” as fat. It can use stored glycogen and fat to meet energy requirements when needed.

Fat

Fat is another energy source for equines. Like carbohydrates, fat is made up of carbon, hydrogen, and oxygen. Fat is a more concentrated energy source than those normally fed to equines (carbohydrates and protein), supplying about 2.25 times more energy per gram than either carbohydrates or protein. Fat sources for equines can have plant or animal origins.

In the past, horsemen believed that equines could not digest and utilize fat well. But studies now indicate that horses can digest and utilize fats from both plant and animal sources quite well.

Equids can utilize fat and oils from plants more easily than fats from animal sources (usually animal by-products). Plant oils can provide the horse approximately three times as much energy as can grains (in comparisons based on equal weight of product). The amount of energy varies somewhat depending on the plant and/or grain source.

The average equine diet contains very little fat compared to the average human diet. Nutritionists typically recommend that human diets have 30% or less total fat content. Most equine feeds contain very small amounts of fat—approximately 2.0% to 3.5%. Even “high fat” equine feeds typically contain no more than 8% to 10% fat.

For example: One cup of corn oil provides about four times the energy supplied by the average equine commercial grain product, based upon weight (the weight of one cup of corn oil compared to an amount of commercial grain equaling the weight of the corn oil).

Pros and Cons of Fats

Adding fat to the equine diet has been proven to increase growth, performance, reproductive function, and milk production.

Equine diets should not contain more than 20% total fat. Research indicates that there might be advantages to feeding horses some fat in place of some carbohydrates in the diet:

no negative effect on the pH of the cecum—this helps to maintain healthy microbes and decreases the chances for colic and laminitis;
increased performance, especially in racing or activities such as barrel racing, which require great use of energy for short periods of time.

Fat in the equine diet helps carry the fat-soluble vitamins through the horse’s digestive tract. Fat is digested mainly in the small intestine. Horse owners know fat is a good energy source for equines.

As with any alterations to a horse’s diet, take precautions when adding fat or substituting fat for some carbohydrate content. Make changes gradually over a period of time.