Magnesium Oxide (MgO) is a scientifically proven quality source of magnesium supplementation for horses – very high 57% magnesium
This is a very high quality grade of magnesium oxide with a high level of magnesium and very low level of iron. For this reason, the price of this premium MgO may be higher than elsewhere. Buyer beware, MgO varies in quality. Balanced Equine only sells premium quality.
Small: net weight = 2.9 kg
Large: net weight = 4.9 kg
Recommended feeding rate is 10 to 20 grams – about 1 metric tablespoon.
Balanced Equine does not recommend excessive supplementation of magnesium in horses – more is not better. Some excess magnesium is excreted but levels in the kidney and bone will rise. Excess may lead to depressed calcium and phosphorus uptake, intestinal, renal and heart issues. Never supplement sufficient magnesium to cause a horse to have diarrhoea.
Magnesium along with calcium and phosphorus are known as the major minerals. Copper, zinc, iron, manganese, selenium and iodine are trace minerals. In a horse’s nutrient intake, either magnesium can be at too low a level compared to the NRC (National Research Council) daily recommendations AND/OR the calcium to magnesium ratio can be too high. Whichever one applies, the diet won’t be optimal.
The symptoms of a magnesium deficiency are the same as for excessive ionised calcium compared to magnesium. Symptoms include muscular symptoms from twitching to spasm, irritability, hypersensitivity, with a potential for intestinal symptoms and heart irregularity when severe. In more extreme cases, a horse can have gait disturbances, including stilted gait, base wide gait behind, difficulty controlling the hind end when turning and reluctance or inability to canter.
Magnesium has many different jobs to do in the body and one of the most important jobs is to control the movement of calcium along calcium channels in cells. The movement of calcium through calcium channels forms the basis for all ‘excitable’ tissue activity, including the nervous system, heart, skeletal muscle and smooth muscle in the intestinal tract, uterus, urinary tract and blood vessels. Magnesium controls the sensitivity of the calcium channel, and is also required for the production and storage of the energy packets (ATP) that is needed by the sodium-potassium pumps to do their job of clearing the calcium from the cell and put it back into storage sites.
Magnesium is involved in so many body processes it is difficult to think of anything that doesn’t involve magnesium. For an excellent review, see: Linus Pauling Institute, Oregon State University
There is zero evidence to support the claim that MgO causes enteroliths. Enteroliths have been linked to intakes high in lucerne and alkaline drinking water.
Some examples of magnesium studies
Magnesium and the oxidative stress
Magnesium and the inflammatory response: potential pathophysiological implications in the management of patients with aneurysmal subarachnoid hemorrhage?
Comparing magnesium mineral sources
Magnesium oxide (MgO) vs Magnesium chloride MgCl2 – When it comes to magnesium in horses, there is no authoritative study that has been done comparing magnesium absorption for all magnesium sources. Dr Eleanor Kellon VMD recommends either the best quality (lowest contaminants/iron) magnesium oxide or magnesium carbonate (MgCO3). We are fortunate to have premium quality MgO in Australia. Another source is magnesium chloride which is a comparatively poor source of magnesium if measured by %. A high quality MgO is around 57% Mg, magnesium carbonate is 25% Mg and magnesium chloride is about 11.7% Mg. There is no evidence that the uptake in horses is better than other sources.
DD Harrington and JJ Walsh published a study that documented 70% absorption for magnesium oxide in the horse, same for magnesium carbonate and magnesium sulfate.
Equine magnesium supplements: Evaluation of magnesium oxide, magnesium sulfate and magnesium carbonate in foals fed purified diets. Equine veterinary journal 12(1): 32-33.
Unfortunately the study is not available free online. Quote from study: “Results of all parameters evaluated indicate that MgO, MgSO4 and MgCO3 are essentially equivalent as supplementary dietary sources of Mg for growing foals. Mean apparent Mg absorption was approximately 70 per cent for all supplements compared to 40 to 60 per cent for Mg in natural feeds fed to mature ponies (Hintz and Schryver 1972)”.
Note: Best not to use magnesium sulfate (MgSO4 – Epsom salts) as the sulfate can give horses diarrhoea.
In rats, it was found to be about the same when comparing MgO and MgCl2. This factsheet by Dr Nerida Richards has a description of the study:
MgO is a nutritional supplement product for inclusion in horse’s feed. Product has no therapeutic effect and is designed to be administered in a feed for voluntary ingestion for horses.
Horse consumption only.