Epsom salt (Magnesium Sulphate) is a clear, colourless and odourless crystalline powder, that when dissolved in water, it is a powerful saline purgative which can be administered orally to Cattle, Sheep, Goats, Pigs, Horses, Dogs and Poultry. It can be absorbed through the skin and has shown benefits in treating swollen muscles and ligaments, bites, cuts and grazes when applied to the skin of affected animals. It also can work as a laxative and as an electrolyte replacer for calves. However most farmers who use epsom salts will feed it to dairy cows to prevent or cure grass tetany. To prevent grass tetany it is suggested that you give 10-15g a cow a day for 3-4 weeks before calving until 12-14 weeks after calving.