2001 S. Lincoln Ave. By Joseph Hahn Information Specialist University of Illinois College of Veterinary Medicine Selenium, in conjunction with vitamin E, is necessary for proper functioning of the immune system and to protect the integrity of cell membranes. However, there is a delicate balance between too little selenium and too much. But in the proper quantities, it is very safe and effective. Selenium is a mineral found in the soil in many areas of the country.
Horses normally ingest selenium while foraging.
It can affect the heart muscle, the muscles of respiration, as well as the large muscles of the back and limbs. It can also cause a decrease in the efficiency of the immune system, leading to opportunistic infections. A horse that has rhabdomyolosis will have severe muscle cramps resulting in sweating, stiffness, and increased pulse. The breakdown of muscle cells can result in coffee-colored urine. While selenium deficiency is not related to the time of year or the horse's sex, it is especially a problem in growing horses.