Grass Tetany (cattle), grass staggers (sheep) and hypomagnesaemia are names given to a condition that can effect stock in late autumn, winter and spring. It can cause significant losses in production, even when there are no signs of illness. Grass tetany or grass staggers occurs when animals are grazing pasture which has low available levels of magnesium, or as a result of increased body demands for magnesium during lactation or late pregnancy. Symptoms of the disease include restlessness, staggers, an over-alert appearance, being excitable and in some cases, aggressiveness. In severe cases, animals may fall down and go into convulsions or die without warning. Prevention is preferable to treatment as grass tetany often occurs without warning. Prevention involves supplementing the animals with magnesium during the period of greatest risk. Olsson’s Beefmaster is the supplement to eliminate the deficiency with 111g/kg of available magnesium.