Minerals are required in higher amounts in a horse’s diet are often referred to as macro minerals. Although there are several, which we will review here, the most frequently discussed when it comes to horses are calcium and phosphorous. There are a variety of reasons why calcium and phosphorus are often viewed as the most important of the macro minerals, so we will talk about them first.
First off, calcium makes up about 35% of the bone structure of a horse. It is therefore critical that sufficient calcium is present in the diet. Calcium deficiency is most probably the number one cause of developmental orthopedic diseases in young horses. Diseases like epiphysitis, OCD and angular limb deformities can all be linked to, among other things, calcium deficiency in young horses. Calcium deficiency can also play havoc with adult horses, especially broodmares, because a horse can actually extract calcium form its own bones when it does not receive enough in its diet, thus weakening the skeletal structure and leading to poor health.
Another important fact about calcium is that horses are very good at regulating the amount of calcium they absorb, as long as it is available at a sufficient quantity. The key, therefore, with supplementing is to make sure that enough calcium is always present for the horse. The natural metabolic processes of absorption and elimination will take care of the rest. In other words, it is far more damaging to a horse’s health to receive too little calcium than too much.
But, of course, there are other important considerations. They are phosphorus and magnesium.
Phosphorus and calcium compete for the same absorption sites in a horse’s digestive system, and if there is too much phosphorous in the diet it actually decreases the availability of calcium. Nutritionists generally agree that the ideal ratio of calcium to phosphorus in a horse’s diet is about 2:1, although even ratios as high as 6:1 have been shown to cause no observable problems for a horse. In essence, what you should worry about is having too much phosphorus as it relates to calcium.
Phosphorus is nonetheless critical to a horse’s overall health. It makes up about 15% of the bone structure and is also necessary for the basic energy reactions within a horse’s system. Just as with calcium, phosphorus deficiency can contribute directly to enlarged joints and crooked legs, especially in young horses.
When supplementing, one should consider the basic forage of the individual horse’s diet. Alfalfa and other legume hays tend to be higher in calcium than phosphorus, so a supplement that has a calcium to phosphorus ratio of approximately 1:1 is appropriate to keep that balance. Grass hays, however, tend to be much lower in calcium, so a supplement that has a calcium to phosphorus ration of 2:1 or even 3:1 will serve the horse’s health better by increasing calcium availability.
As it relates to calcium, magnesium aids in the absorption of calcium when it is available in sufficient levels in a horse’s diet. Magnesium is also critical to normal muscle functioning in horses. Some observations show that proper magnesium levels can also have a “calming” effect on a horse by eliminating nervousness and flightiness that arises from poor muscle function. It also serves as an activator for a wide range of enzymes in a horse’s body.
Sodium plays a variety of important roles in a horse metabolic processes. It helps transport substances such as amino acids across cell membranes. It also helps moves signals throughout the nervous system, assisting with the activation of cellular impulses. Sodium is one of the major electrolytes and thus helps regulate the use and location of body fluids within a horse. And on a very simple level, the intake of sodium by a horse induces thirst, leading to higher water consumption, which leads to better digestion and better overall health through adequate hydration at all times of the year.
Potassium, another of the major electrolytes, is closely related to sodium in its functions. It is critical in the activation of muscles cells, and fully 75% of the potassium in a horse’s body can be found in its muscle tissue. When a horse moves any part of its body, it is using potassium. This includes the heart muscle. As with many of the other macro minerals, a horse is very good at eliminating excess potassium as long as it has sufficient water. Potassium can be lost through sweating when a horse is particularly hot or working hard, so a supplement with appropriate levels of potassium may be particularly important when a horse is exercising, performing or working for long periods of time or in hot weather.
Most people don’t think of chlorine as a mineral, but it is, in fact, a necessary component of a horse’s metabolic system. Chlorine is an important part of the bile made by the liver, which assists in digesting fat as it is secreted into the large intestine from the gall bladder. Chorine is also part of hydrochloric acid, which is found in the stomach at one of the first steps in digestion. It also helps control the pressure of fluids that exist outside the cellular structure.
Sulfur is found in many of the important substances that are essential to a horse’s health. Among them are insulin, biotin, chondroitin, heparin and several of the essential amino acids, such as methionine and cystine. Sulfur is also critical in the formation and maintenance of a horse's joint tissues.