Ultra-Sel Combines optimal selenium absorption and high bioavailability vitamin E with multi-plex Magnesium, a proprietary brand of magnesium to support muscle metabolism. This unique blend provides quick absortpion into the stomach as well as sustained absoption. Supports reduced risk and alleviation of tying-up. Product Details: Palatable 99% pure selenium Chelated organic magnesium Supports optimal performance serum selenium level Supports reduced PSSM (Polysaccharide Storage Myopathy) Supports improved muscle metabolism Great for horses experiencing muscle soreness or prone to tying up For horses in low selenium areas