Magnesium is an important major mineral which is needed in the horse's diet. Magnesium, along with calcium, phosphorous, sulfur, sodium, chloride, and potassium make up the major minerals required in the horse's diet. They are known as the 'major' minerals not because they are more important, but because they are needed in larger (gram) amounts as compared with the trace minerals. Magnesium is essential for a host of functions in the horse's body, from controlling the movement of calcium in the proper channels to keeping blood vessels relaxed.
The amount of magnesium (as well as all of the major minerals) needed in the horse's diet will vary depending on body weight, age, specific condition (pregnant, lactating, i.e.), and activity level of the horse. The NRC (National Research Council) has published nutrient requirement tables which indicate amounts of specific minerals needed by the horse. This table should be used as a guideline in feeding supplemental magnesium to the horse. However, before any horse owner feeds supplemental magnesium, he/she should determine the current intake of the mineral by the horse. This can be found by having your forage (grass/ hay) analyzed by a company such as Equi-Analytical and by observing the feed label provided on any manufactured feed given to the horse. Many horse owners mistakenly think that commercial feeds provide the majority of the horse's nutrition, when in reality, it is forage that provides the greater portion of the horse's nutrition.
Magnesium Deficiency
Magnesium deficiency symptoms mirror those of excess calcium in the horse. Since the ratio of calcium to magnesium fed to the horse should be 2:1, these two minerals are interdependent. If a horse is deficient in magnesium, it may show irritability, hypersensitivity, twitching or muscle spasms, or at worst, gastro-intestinal problems or heart irregularity. Many horses with a magnesium deficiency are misdiagnosed by vets as having EPSM.
Magnesium as a Stress-Reducer
Magnesium plays an important role in the function of the nervous system, and an excess or deficiency of the mineral can affect the behavior of the horse. Dr. Eleanor Kellon V.M.D. has performed field trials using supplemental magnesium for horses who displayed nervous behavior. She reported that while results varied depending on the specific problem displayed by the horse, magnesium had a noticeable effect on horses with anxiety, spookiness, and overreaction to sound or touch. She also noted that "aggressive horses were less easily provoked" when fed supplemental magnesium. Magnesium is a safe supplement, carrying no long-term side effects for the horse. It does not 'drug' the horse or change its blood chemistry at all.
Magnesium and Laminitis
Magnesium has also been studied for its effects on chronic laminitis in the horse. Human studies have shown that supplemental magnesium can benefit insulin resistance, and the same appears to be true for horses with laminitis. Dr. Kellon has observed changes in foot comfort, obesity, and abnormal fat deposits when magnesium was supplemented for horses with this condition. 3-5 grams of magnesium a day is a safe dose, but again, each horse's diet should be analyzed for the proper dosing of magnesium.
Magnesium is only one of the major minerals needed in the horse's diet, but it plays a critical role in many functions of the horse's body. If you suspect a magnesium deficiency in your horse, have your horse's diet analyzed (remember, forage is just as, if not more important than commercial feeds), and determine how much magnesium is already being provided for the horse. Supplemental magnesium can be purchased from companies such as Horsetech. Also, take the calcium intake of the horse into consideration. If the calcium-magnesium ratio is out-of-balance, changes must be made in the horse's diet to insure a 2:1 (Ca: Mg) ratio.
Sources
- Kellon, Eleanor V.M.D. Horse Journal: Guide to Equine Supplements and Nutraceuticals. Guilford, CT: The Lyons Press; 2008.
- Kellon, Eleanor V.M.D. "The Major Minerals." NRC-Plus. 2008.
