Here's a good article, http://www.horsetalk.co.nz/health/magnesium-121.shtml I wouldn't use it. Too easy to use too much, resulting in diarrhea. Most horses are going to get sufficient Mg in their forage. The other 50 to 77% is water. Carla RichardsonOn Tue, Nov 3, 2009 at 10:57 AM, Don Huston <donhuston@xxxxxxx> wrote: Can I add Epsom Salt (9.8%Mg 12.9%S) to my electrolyte mix? Howmuch is a safe dose? What is the other 77% in Epsom Salt? Thanks, Don Huston =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Ridecamp is a service of Endurance Net, http://www.endurance.net. Information, Policy, Disclaimer: http://www.endurance.net/Ridecamp Subscribe/Unsubscribe http://www.endurance.net/ridecamp/logon.asp Ride Long and Ride Safe!! =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=