Magnesium sulfate is an odorless solid that is generally found as needle-like colorless crystals or as a white crystalline powder (Kawamura and Rao, 2007). The substance is considered very soluble in boiling water. Magnesium sulfate is usually obtained directly from dry lake beds and other natural sources. It can also be prepared by reacting magnesite (magnesium carbonate, MgCO3) or magnesia (oxide, MgO) with sulfuric acid. Magnesium sulfate is used both externally (as Epsom salt) and internally. The main external use is the formulation as bath salts, especially for foot baths to soothe sore feet. Such baths have been claimed to also soothe and hasten recovery from muscle pain, soreness, or injury. Internally, magnesium sulfate may be administered by oral, respiratory, or intravenous routes. Internal uses include replacement therapy for magnesium deficiency, treatment of arrhythmias, preventing eclampsia, a tocolytic agent, and as an anticonvulsant.
Action
Magnesium is necessary for all reactions in the body that require energy. As the second most abundant intracellular cation, magnesium acts as an activator or catalyst in enzymatic reactions. Magnesium forms a complex with adenosine triphosphate. Bone and skeletal muscle contain the highest levels of magnesium of any organ system. Low levels of magnesium are also stored in the blood. In the blood, magnesium is in free form or is bound to serum proteins (mostly albumin), citrates, phosphates, or other compounds (Cornell University, 2006).
A balance between intestinal absorption and renal excretion is important in preventing levels of magnesium from becoming too high in the body. Serum magnesium levels are controlled by the kidneys, and the glomerulus within the kidney filters 70–80% of plasma magnesium. Reabsorption of magnesium depends on many factors, including hormone levels (e.g., parathyroid hormone, antidiuretic hormone, calcitonin, thyroxine), serum levels of calcium and magnesium, and an individual’s dietary content. Magnesium is also secreted in the saliva of ruminants and in the sweat of horses (Cornell University, 2006).
Hypomagnesaemia is the result of an insufficient intake of magnesium. Clinical signs include convulsions and muscular spasms, and death may occur due to respiratory failure. In order to increase the uptake of magnesium, livestock feed can be supplemented with magnesium sulfate. In scenarios where immediate treatment is needed, livestock can be injected intravenously with a solution of magnesium sulfate (Organic Livestock Research Group, 2000).
Importance in Veterinary
Magnesium sulfate has a number of veterinary uses. It acts as an anticonvulsant, laxative, bronchodilator, electrolyte replacement aid with hypomagnesaemia, and may be used to treat cardiac arrhythmias. Specifically in swine, magnesium sulfate is administered to treat malignant hypothermia (Dodman, 2010). Magnesium sulfate is used for constipation and bowel evacuation prior to certain procedures. A dose of 1-2 mEq/kg of magnesium sulfate produced plasma concentrations of 8.5-12.2 mEq/L, and can increase heart rate, inotropy, and cardiac output.
Magnesium sulfate is added as a source of magnesium to livestock feed when levels of magnesium are low in pastures to treat conditions stemming from a magnesium deficiency (Adnani, 2010). Lactation tetany or grass tetany occurs when ruminants graze on grasses low in magnesium or suffer from a low level of magnesium in their diet. The condition is often realized after cases of sudden death in cattle. Clinical signs include convulsions and muscular spasms, and death may occur due to respiratory failure (Organic Livestock Research Group, 2000). If livestock are feeding on pastures with high potassium levels, which interfere with the uptake of magnesium by grasses, supplemental magnesium sulfate may be needed (Epsom Salt Council, 2009). Dairy cows and other livestock suffering from hypocalcaemia (or milk fever; characterized by reduced levels of calcium in the blood) are usually deficient in calcium as well as magnesium. Combined treatments of calcium borogluconate and magnesium sulfate have been observed to be effective (Organic Livestock Research Group, 2000).
Magnesium capsules can be inserted into the rumen of livestock and after a one-week stabilization period, the capsule begins to release magnesium for up to 80 days. This capsule is recommended for use in high-risk or valuable animals. It is advised that, in addition to the capsule, the livestock be fed hay in order to increase absorption of the magnesium (Champness, 2007). If immediate treatment for magnesium deficiency is needed, magnesium sulfate can be administered intravenously (Papich, 2007).
A magnesium lick can also be provided for livestock to increase the amount of magnesium in the diet. Because magnesium sulfate is not palatable, molasses is added to the magnesium lick to encourage cattle’s use. Licks are generally 80 percent molasses and 20 percent magnesium sulfate and are considered to be less reliable than supplementing feed with magnesium (Harris, 2005).
Epsom salt, a common form of magnesium sulfate, is easily dissolved in water and is used to relieve muscle aches and pains as well as to reduce itching and inflammation. For humans, it is commonly added to bathwater and used by individuals suffering from joint pain (Epsom Salt Council, 2009). Epsom salt can be used to treat inflammation and abscesses in livestock as well (Clarkson, 2007). Soaking the affected area in a mixture containing Epsom salt and water can reduce signs of inflammation (Epsom Salt Council, 2009). Ingestion of a large volume of water containing magnesium sulfate is not recommended as magnesium sulfate is known to have laxative effects (Epsom Salt Council, 2009). Dairy cows and other livestock suffering from hypocalcaemia (or milk fever; characterized by reduced levels of calcium in the blood) are usually deficient in calcium as well as magnesium. Combined treatments of calcium borogluconate and magnesium sulfate have been observed to be effective (Organic Livestock Research Group, 2000).
Urfeya Mirza*, Uiase Bin Farooq, D.M. Makhdoomi
1Division of Veterinary Surgery and Radiology, FVSC&AH, SKUAST-K