What Are Calcium & Phosphorus Used for in Horses?

Both young and adult horses need ample calcium in order to keep their bones strong and healthy. Equine calcium absorption, however, is directly affected by how much phosphorus is in a horse's diet, so it's important to ensure the feed you give your horse contains the correct balance of these two minerals.

  1. Calcium

    • Calcium is one of the most important minerals in a horse's diet, as many parts of a horse's body require calcium. One of these is the horse's bones, which make up about 35 percent of a horse's total body weight. Calcium plays other roles in a horse's body, such as activating muscle contraction, aiding the function of cell membranes, and regulating enzymes throughout the body. Absorption of calcium, however, is influenced by the presence of other minerals, particularly phosphorus.

    Phosphorus

    • If a horse's diet contains too much phosphorus, this will cause a reduction in how much calcium the horse's body will absorb. This is because both minerals are absorbed by the same area in the horse's small intestine, causing these two minerals to compete to be absorbed. It's important, therefore, that phosphorus levels be kept in the proper balance with calcium intake, as an incorrect ratio can have a negative impact on both adult horses and young horses that are still growing.

    Ratio

    • In order for calcium to be absorbed efficiently, every gram of phosphorus a horse ingests must be matched with a gram of calcium; if a horse doesn't ingest sufficient calcium, its body will draw calcium from wherever it can, such as calcium stored in the bones. Too much phosphorus and not enough calcium will result in a horse's bone integrity becoming compromised. When determining a horse's diet, it's crucial to ensure that every gram of phosphorus the horse takes in is balanced by at least an equal amount of calcium, if not more --- although excessive levels of calcium (greater than seven parts calcium to one part phosphorus) are not recommended.

    Achieving a Balance

    • Maintaining this ratio can be problematic considering most grass hays used for horse feed only contain low to moderate levels of both minerals. Most cereal grains, on the other hand, are low in calcium but high in phosphorus. A horse fed grass hay and large amounts of grain could easily ingest less calcium than phosphorus. It's important to choose the right feed and either decrease a high-phosphorus feed or eliminate it all together and replace it with a feed that provides less phosphorus and more calcium until you achieve the desired ratio.