Two of the most common conditions that occur in pregnant and nursing beef cows in the spring with lush pastures are grass tetany and milk fever.  Unusual behavior, unsteady gait, and difficulty rising are all signs that can be related to grass tetany.  The condition usually occurs in cows in early lactation and is due to inadequate magnesium in the diet. Magnesium is necessary for nerve contraction and muscle function.  Dr. Paul Beck from Oklahoma said at drovers.com that cattle with grass tetany become excitable, develop muscle tremors, have difficulty breathing, and in some cases will die.  Cattle with grass tetany are likely to be very aggressive towards humans so be careful checking these cows. After successful treatment, they may try to run you over.  Use caution when running these cows through the chute to treat them as excitement will cause many to go down and seizure. 

To determine if the pasture is at risk for grass tetany, forage testing for calcium, phosphorus, magnesium, potassium, sodium, and sulfur can be performed. A ratio greater than 2.2 potassium to calcium and magnesium is likely to result in grass tetany.  Wheat and oat pastures are a big risk because rapidly growing pastures have increased potassium which blocks the uptake of magnesium.  Lactating cattle also lose magnesium through the milk so if they are not getting enough magnesium from the diet, grass tetany can occur.  Treatment of cattle with grass tetany includes an intravenous infusion of calcium and magnesium and removing the animal from the susceptible pasture.  Prevention of grass tetany requires feeding a high magnesium mineral with 10-12% magnesium oxide and each cow must ingest 3-4 ounces per day.