Most disorders of magnesium metabolism are due to problems associated with absorption of the mineral from the digestive tract. The differences in anatomy between species are associated with the importance of disorders of magnesium occurring in a particular species. In horses, disorders of magnesium metabolism are much less common than in cattle and sheep, in which magnesium is mainly absorbed from the rumen in adult animals. Horses are able to absorb magnesium from the small intestine. Too much magnesium in the blood (hypermagnesemia) is rare, but horses receiving excessive doses of magnesium sulfate for constipation may show signs of sweating, muscle weakness, and rapid heartbeat and breathing rate. Cardiac arrest can occur with very high blood magnesium levels.
Last full review/revision July 2011 by George M. Barrington, DVM, PhD, DACVIM; David L. Evans, BVSc, PhD; Katharine F. Lunn, BVMS, MS, PhD, MRCVS, DACVIM; Donald C. Sawyer, DVM, PhD; Ivan W. Caple, BVSc, PhD, MACVSc, MRCVS; Sharon J. Spier, DVM, PhD, DACVIM