Like a gleaming coat, healthy hooves are a reflection of a horse's overall state of health and nutritional status. Common factors affecting the quality of the hoof are genetics, environment, correct trimming and nutrition. Optimal nutrition, based on the horse's needs, is a key element in encouraging strong, healthy hooves.

Horses evolved as constant grazers of high fiber, low energy forage. Many health problems, such as colic and laminitis can be avoided by keeping the horse on a simple, free choice grass hay diet. The equine digestive system is designed to break down fiber by means of microbial fermentation in the large intestine. Fiber can be a significant source of energy for the horse and many moderately worked horses can obtain all of their energy needs from quality hay alone. Some grass hays may contain surprisingly high levels of sugar. Horses that are easy keepers or insulin resistant should be fed low sugar hay. Sugar and starch content can be tested by sending a sample to a forage testing laboratory.

Horses that work hard or are involved in sports that require high levels of energy, such as endurance or combined training, will perform best with a higher carbohydrate diet, including grains. Carbohydrates from grains (starches) are digested by enzymes in the small intestine and converted into glucose for readily available energy. Grains need to be slowly introduced to the horse's diet in order to avoid carbohydrate overload, which can result in colic or laminitis. When the horse's workload is reduced for any reason, the grain portion of the diet needs to be reduced accordingly.

Protein is required for growth and tissue repair. Excess protein can be converted to energy, but it is an inefficient process compared to carbohydrates. Protein requirements increase slightly with exercise, but the protein-to-calorie ratio does not. Although there are 22 different amino acids that are needed for protein synthesis, several can be made by the tissues of the body. There are 10 that must be supplied to the horse ­ lysine, methionine, arginine, histidine, isoleucine, leucine, phenylalanine, threonine, tryptophan, and valine. Lysine is commonly deficient in grass hay rations and must be supplimented in the diet, particularly for growing horses. Mature horses at maintenance are less sensitive to protein quality than growing horses, but protein needs should never be overlooked. According to the National Research Council (NRC) guidelines, a mature horse needs approximately 21 grams of lysine daily for maintenance. At best, grass hays only contain .1 - .2% lysine, however, 6 lbs. of alfalfa could supply the lysine needs of that horse. While alfalfa hay is a good source of lysine, lysine may also be supplemented by adding other feeds, such as beet pulp, flax, rice bran and sunflower seeds. Methionine is another amino acid that is important for healthy hoof growth and, like lysine, is usually deficient in grass hay diets. Alfalfa, beet pulp, flax, rice bran and sunflower seeds are good sources. The actual requirements for methionine in the horse are not known at this time, but have been estimated to be roughly 25% of the levels for lysine.

A horse's natural diet is very low in fat. Most grass hays are less than 3% fat. Horses do require certain essential fatty acids (EFAs), however. Omega 3 and 6 are important for good health. Most horses get sufficient omega 6 in their diets, but unless they have access to green grass, omega 3 needs to be supplemented. 2 oz. daily of freshly ground flax seed will supply sufficient levels of omega 3 fatty acids. Rice bran is a good source of omega 6. A 50-50 ratio of 3 and 6 seems to work well for most horses. Horses that are prone to allergies, such as sweet itch (gnat bites) often respond well to the addition of ? cup of ground flax seed to the daily diet.

Adding corn oil or other supermarket oils to a horse's diet is a popular means of increasing calories without adding carbohydrates. These oils, however, do not supply essential fatty acids. Processing of oils to be stable on a store shelf destroys fragile EFAs, as does exposure to light, heat and oxygen. Corn oil is pure fat ­ nothing else. Fat builds fat ­ not muscle, bone nor connective tissue. While horses are able to digest and utilize high fat diets, it is best to avoid them for the serious athlete.

Minerals are involved in many bodily functions, such as formation of bone and connective tissue, hormones, metabolism and energy use. A proper balance of minerals is also important in hoof growth and quality.

Calcium and phosphorus and their ratio to each other are related to normal hoof development. Calcium is needed for laminar attachment in the hoof horn. Excess phosphorus can block the absorption of calcium from the small intestine. This can result in a calcium deficiency and cause weak and abnormal bones.

Magnesium is important for a properly functioning nervous system, metabolism and energy regulation. Magnesium deficient diets can induce insulin resistance, while magnesium-rich diets may prevent it. In fact, the effect of magnesium is so strong that deficiencies may even cause type II diabetes in people who have no genetic predisposition for it. Magnesium deficiency and insulin resistance are also very commonly found in horses that are extremely "easy keepers", obese, with abnormal fat deposits like large crests or hard lumps of fat at odd places on their bodies. High calcium diets interfere with absorption of magnesium. Ideally, aim for a 2:1:1 ratio of calcium to phosphorus and magnesium.

Trace minerals include iron, copper, zinc, manganese, iodine and selenium. These minerals are referred to as "trace" because they are only needed in very small amounts by body, but they are very important. Certain trace minerals need to be in the correct ratios with each other, in addition to the proper amounts. Too much of one can interfere with absorption of another. For instance, high levels of iron will block absorption of copper and zinc. A good ratio to aim for is 4:4:4:1 for iron, zinc and manganese to copper.

Some trace minerals, such as selenium have a fairly narrow margin of safety. The horse needs selenium for normal muscle function and normal function of the immune system.

Toxicity is characterized by loss of appetite, loss of mane and tail hair, and in the severe form, blindness, loss of the hoof wall, paralysis, and death.

Excesses of iodine will produce the same symptom (goiter) as too little. Iodine is essential for the synthesis of thyroid hormones that regulate metabolism. Kelp is a very rich source of iodine and a horse regularly fed kelp based supplements may run the risk of iodine excess.

How do you know if your horse needs supplementation? Start with the greatest part of your horse's diet ­ hay. Most full sized adult horses consume 15 ­ 20 lbs of hay per day. If you can, you should obtain an analysis of your hay and determine what is in it. You simply cannot tell by looking at it or going by what kind of hay it is. Sure, we know that alfalfa is usually high in protein and calcium compared to grass/cereal hays, but other nutrients can vary widely depending on soil and growing conditions. Since I started testing local hay two years ago, I have accumulated some interesting data on common deficiencies and excesses in Butte County hay. UC Davis did a study on beef cattle that documents trace mineral levels in California soils and is applicable to forage grown for horses. Another good source for data about hay is the Equi-Analytical Laboratories website.

The most common finding in California hay is high iron/manganese and very low copper and zinc. Excess iron is not a good thing for horses and can interfere with copper absorption, which is already in short supply. To make matters worse, feed companies often load their products with additional iron. I tested one well known brand of senior feed and found that the iron levels were over twenty times higher than what they should have been according to NRC guidelines. Another product by the same company also tested very high in iron, even though no iron was listed in the ingredients. Feed companies are NOT required to list iron levels on their tags, so a consumer has no way of knowing how much iron is in a product without the expense of sending a sample off to the lab.

Before you decide to shop for a supplement, read the National Research Council book, "Nutrient Requirement of Horses". Understand what your horse does or doesn't need. Many expensive products are full of ingredients that your horse might not need or benefit from. You can print a copy of the NRC recommendations for your horse, according to age, weight and activity level, by going to http://www.nap.edu/books/0309039894/html/

Listed below are the recommendations for a mature 1,000 lb. horse at maintenance.

Class: Maintenance Horse
Body Weight (lbs): 1,000
REQUIREMENT BASIS

NUTRIENT	Total	Percent
DRY MATTER INTAKE	16.5 lbs/day	1.65 % of Body Weight
DIGESTIBLE ENERGY	15.0 Mcal/day	0.91 Mcal/lbs
CRUDE PROTEIN	600 grams/day	8.00 %
LYSINE	21.0 grams/day	0.28 %
CALCIUM	18.1 grams/day	0.24 %
PHOSPHORUS	12.7 grams/day	0.17 %
MAGNESIUM	6.8 grams/day	0.09 %
POTASSIUM	23 grams/day	0.30 %
SODIUM	7.5 grams/day	0.10 %
IRON	300 mgs/day	18.14 mg/lbs
ZINC	300 mgs/day	18.14 mg/lbs
COPPER	75.0 mgs/day	4.54 mg/lbs
MANGANESE	300 mgs/day	18.14 mg/lbs
IODINE	0.8 mgs/day	0.05 mg/lbs
COBALT	0.8 mgs/day	0.05 mg/lbs
SELENIUM	0.8 mgs/day	0.05 mg/lbs
VITAMIN A	13,608 IU/day	822.57 IU/lbs
VITAMIN D	2,251 IU/day	136 IU/lbs
VITAMIN E	375 IU/day	22.7 IU/lbs

The nutrient requirements for horses is based upon the National Research Council Nutrient Requirements of Domestic Animals, "EQUINE Nutrient Requirements (1989)"