by Paul D. Siciliano, PhD Colorado State University Fort Collins, Colorado
Horses require approximately 22 different nutrients in their diets. These nutrients can be classified into energy-supplying, protein and amino acids, vitamins, minerals and water. A balance among these nutrients is important to ensure adequate levels to support the major physiological functions in the horse. Although all of these nutrients are important, those that supply energy are crucial because they drive many of the metabolic processes involving the other nutrients. Therefore, a means for assessing the energy balance of a horse can be quite useful to monitor the effectiveness of a feeding program.

The energy balance of a horse is reflected by its degree of body fat covering and can be classified as positive, negative or neutral. A positive energy balance exists when the energy intake exceeds that required, causing the horse to store excess energy in the form of body fat. A negative energy balance implies that the horse is using more energy than is being supplied by the diet. As a result, the horse draws energy from body reserves (i.e. fat stores) and, in severe cases, from skeletal muscle proteins. In either case, the horse will lose weight and eventually become emaciated. A neutral energy balance indicates that the amount of energy consumed is equal to amount used.

A scoring system has been devised (Henneke, et al., 1983) to define horses in various body conditions, allowing the horse owner to monitor body condition over a long period of time and determine whether the diet is resulting in a positive, negative or neutral energy balance. The scores range from one (emaciated) to nine (obese). A condition score of five is termed moderate and is the target for most classes of horses. A body condition scoring chart is located on page 4.

Note: a condition score of no less than five is extremely important for the broodmare. Research has indicated that broodmares having a condition score of less than five show decreased reproductive efficiency (i.e. low conception rates, increased early embryonic mortality).

To achieve a condition score of five, modifications to the diet are often necessary and can be as simple as changing amounts and types of feeds. Some general suggestions for increasing or decreasing body condition scores of mature horses are outlined below. To increase body condition score:

- Feeding a higher quality forage in amounts equaling approximately 2.5 pounds of forage per 100 pounds of body weight will increase the energy density in the diet. The new forage should be introduced slowly over a period of approximately three weeks to avoid digestive upset (see Equine Sciences Newsletter, Winter 1998 for article on forage quality).
- Concentrates (cereal grain mixes fortified with vitamins and minerals) are much higher in energy density than forages and can be added (up to 40% of the total diet, maximum of 8-10 pounds) to increase the energy density of the diet. However, amounts ranging from 3-5 pounds are generally adequate for providing extra energy necessary to increase body condition. Care should be taken when introducing concentrates into the diet to prevent overfeeding, which may result in colic or laminitis. Concentrates should be introduced at amounts of 1-2 pounds per head for approximately one week with a gradual increase of approximately one pound every three days, but no more than a two-pound increase per week. If the total daily amount fed exceeds 4 pounds, it should be divided into two equal feedings. Because of the many different concentrates are available, consulting your feed dealer for the concentrate best suited for your horse is recommended.
- Adding fat to the diet in the form of soybean and corn oil can also increase the energy density of the diet. Fat can be added up to approximately two cups per day. It should be divided into two equal feedings and applied to the concentrate. If no concentrate is currently being fed, a small amount (1-3 pounds) should be added to the diet to carry the oil. When adding oil to the diet, it is best to begin slowly with approximately ½ cup until the horse is eating well and then increase ½ cup every three days up to 2 cups.

To decrease body condition score:
- Feeding lower quality forages (more mature grass hays) and avoiding high quality legumes (alfalfa) can decrease the energy density of the diet. Although decreasing the amount a horse eats can decrease body weight, forage (hay and/or pasture) amounts should not be dramatically decreased. Horses need to consume a minimum of 1.5 pounds of forage per 100 pounds of body weight per day and feeding too little can lead to digestive upset such as colic. However,
- Cereal grain concentrates should be removed from the diet. However, because concentrates also provide vitamins and minerals, the concentrate should be replaced with a vitamin/mineral supplement complimentary to the forage. In some cases, forages can meet almost all of the requirements of certain classes of horses (i.e. maintenance, extremely light work).
- Forced exercise is also an effective means of decreasing weight on the horse. This should begin gradually with 10-15 minutes of exercise and increased accordingly. However, the soundness of the horse does not always permit this. Changes in body condition should occur in approximately 30-60 days. In addition to modifying the nutrition of your horse, deworming, vaccination, dental care and the availability of adequate water, salt and shelter will also influence response to the changes in diet. Periodically monitoring and recording your horse's body condition can provide a simple and efficient means of assessing the effectiveness of your nutritional program. Dr. Paul Siciliano is an Assistant Professor of Animal Sciences specializing in Equine Nutrition. His research focuses on the nutrient requirements of the growing horse.