Sixty percent to 70 percent of magnesium is found in bones. The rest is in liver, muscle and blood. Magnesium is required for normal skeletal development,nervous and muscular system functions and for enzyme systems. It is also closely associated with metabolism of calcium and phosphorus. In ruminants, a major magnesium deficiency disease is grass tetany, often seen on fast-growing, lush, cool season pastures. Affected animals have low-blood magnesium levels, exhibit a loss of appetite, are excitable, stagger, have convulsions and may die. High-fertilization rates, cool temperatures and high levels of plant potassium and/or rumen ammonia may contribute to the disease. A major supplemental source of magnesium is magnesium oxide. It is often supplemented on winter wheat pasture and mixed with a protein source to encourage consumption.
Reference: Hart, S. 2008. Meat Goat Nutrition. Pages 58-83 in Proc. 23rd Ann. Goat Field Day, Langston University, Langston, OK.