Sources of Energy for Horse Feeds

by Dr. Ron Rompala

A horse needs energy for many reasons. Energy comes from the chemical break-down of carbohydrates, fats and protein. While each of these groups of compounds provide energy, the process by which tissues utilize these substances differs. Excessive utilization of one group of compounds to obtain energy can have a profound effect upon the horse. Problems associated with horses that are prone to tying-up may be due to muscles utilizing too many carbohydrates for energy and not enough fat.

One immediately thinks of carbohydrates as sugar, starches and other compounds that supply the horse with quick energy. Once digested, carbohydrates are broken down to glucose or other simple sugars and subsequently absorbed into the blood. Glucose levels in the blood are tightly regulated. When glucose levels rise, which happens after eating, insulin is secreted by the pancreas. Insulin facilitates the entry of glucose into muscle and other cells. Glucose that is in excess of the immediate needs of the horse goes into adipose tissue and is converted into fat. Once converted into fat, it cannot be converted back into glucose. In spite of all the glucose absorbed after a meal, glucose reservoirs, as glycogen, are limited to liver and muscle. Liver glycogen is primarily used to maintain blood glucose levels hours after a meal. Muscle glycogen is used to fuel muscles when a quick burst of energy is needed.

However, all carbohydrates are not the same. It is often overlooked that fiber is also a carbohydrate. Fiber acts as a structural component in the plant while sugars and starch act as energy stores. Fiber cannot be enzymatically digested by horses. Microbial fermentation in the gut of the horse releases short chain fatty acids that are generally metabolized like fat. Fiber content in the feed is often characterized as crude fiber or neutral detergent fiber. In contrast, starch an sugar are referred to as non-fiber or nonstructural carbohydrates.

Fats are the primary energy source of most cells including muscle. However, there are some limits to the use of fat as energy. Unlike glucose, fat cannot be metabolized under anaerobic conditions. However for reasons not clear, heavy anaerobic use of glucose by muscles can lead to problems. Some are fairly minor as cramps but some can be severe as manifested as tying-up. The performances of horses that are prone to tying-up have been improved by feeding more feeds that are higher in fat. This seems to modify glucose metabolism the extent of keeping the horse from tying-up. Researchers have been interested in the relationship between nutrition and tying-up. Many equine specialist believe that horses prone to tying-up benefit when consuming diets having at least 20% of the energy from fat.

Protein also acts as a source of energy. Some tissues, such as the intestines, use protein as a major source of energy, Increased utilization of protein for energy causes increased urination.

It is possible to roughly determine the contribution of the total energy available to the horse from protein, fats and carbohydrates. Determining the minimum amount of dietary energy from fat can be beneficial for choosing the proper feeds for horses that are prone to tying-up. Contributions of the total digestible energy from fat in Blue Seal horse feeds are estimated as follows:

Feed	Percent of Energy from Fat
Horse 10	10
Strider®	14
Pacer™	20
Rider®	13
Charger®	13
Trotter®	10
Contender®	12
Demand®	23
Hunter™	23
Vintage Racer®	21
Vintage Sweet™	20
Vintage Senior®	20
Vintage Gold®	26
Vintage Mare & Foal	18

© May, 2000. Blue Seal Feeds, Inc.

© Blue Seal Feeds – May, 2000