Water is critical but it’s not in the food pyramid since it contains no calories.

Nearly everyone has seen or heard of the USDA’s food pyramid for people. The original food pyramid gave recommendations for carbohydrates, proteins and fats in "servings," and it was heavily geared to carbohydrates. The newest version, called "My Pyramid" has switched the emphasis to fruits and vegetables, spells out exactly what a "serving" is, and has an interactive active feature that allows you to specify age, sex and activity level to get an individualized plan. Visit www.mypyramid.gov.

If we were constructing a pyramid for horses, the base is unquestionably hay or pasture. We would break that down further into 80 to 90% grasses and 10 to 20% legumes (alfalfa, clover). Although horses can do just fine on 100% legumes, and many have, legumes are mineral imbalanced, have an excess of protein over requirements (leading to higher urine output) and are somewhat more calorie dense, which means less chew time or a weight gain if access is not limited.

This is the horse’s major source of calories, protein, fats, vitamins and minerals. A serving size would depend on the horse’s activity level and how easily it gains/holds weight but, in general, it’s 1.5% to 3% of body weight/day. The lower feeding level is for inactive horses that gain weight easily; higher level for exercising, late pregnancy and lactation.

The only other essential box on our equine feed pyramid is salt. The horse needs a minimum of 1 oz./day of plain, white salt in addition to the hay or pasture. Two tablespoons of plain salt is one ounce. (See page 3.)

For horses on pastures with a variety of grasses and some clover or alfalfa, it’s possible that these two boxes will cover all their needs. However, soil mineral imbalances may cause inadequate amounts of key trace minerals, usually iodine, selenium, zinc and copper in the hay.

So, just to be sure all the bases are covered, we’d put another little box on top with a "possible minerals" name on it, those needed to fill gaps due to common mineral profiles in your area’s pastures (consult your local agricultural agent for these).

Concentrates
Grains are predominantly used for calories. Other concentrated calorie sources are beet pulp, brans and fat. While the minerals in grains can be used to help balance some types of pasture/hay, their usefulness for this is limited by the calories they provide.

Relying on grains to balance the diet or provide supplement "insurance" has a predictable result in most cases: a fat horse. Grains should only be fed when the horse is consuming all the hay/pasture it can eat but is not holding an adequate body condition.

Some nervous horses in "hard-keeper" breeds, like the Thoroughbred, may need some grain even when relatively inactive, but for most horses this simply isn’t the case. The calories in grain come almost all from starch. In human terms, hay is like an all-bran cereal, while grains are more like a piece of cake.

Fats
The natural diet of a horse—pasture—is low in fat, has no more than 5% fat in early growth stages of grass. That is on a "dry-matter basis," meaning 5% of the solid component of the grass, after all water is removed. If we assume the horse consumes about 15 lbs. per day of dry matter, that means 0.75 lbs. of fat (12 oz.) when eating young growths of grass. This drops to 3 to 4% when grass is mature, and usually no more than 3% in hays.

The type of fat is also important. Grasses are high in the essential fatty acids omega-6 and omega-3, with at least four times as much omega-3 as omega-6. Omega-3s are fragile, rapidly destroyed by processing.

Fats contain nothing but calories. No protein, no vitamins and no minerals. Just calories. Stabilized fats, like those added to feeds and corn oil bought on a store shelf, don’t have the types of fatty acids the horse needs.

Protein
Unless the pasture is of poor quality, it will provide a protein equivalent to 10% protein hay. When a variety of plant types are present, this also results in a variety of amino acids.

Although most people think of the horse’s protein needs in terms of a percentage, this isn’t correct. The horse’s protein needs are in terms of grams/day, not a percentage of the diet. A 1,100-pound horse at maintenance needs 656 grams/day of protein. A good pasture will provide this, as will 14.4 pounds of 10% protein hay, 24 pounds of 6% protein hay.

Horses on hay rather than a pasture with mixed grasses may need some vitamin/mineral supplementation. Vitamin E definitely needs to be supplemented for these horses. Vitamin A will be needed if the hay is more than a year old, and, in special cases, C or B vitamins may be advisable.

The less variety there is in the horse’s hay, the more likely it is to contain significant mineral deficiencies or imbalances, and these will need to be addressed as well for a proper diet. However, there are plenty of single vitamin/mineral or multi-ingredient supplements out there that can get the job done (see December 2007 for recommendations).