Predisposing Conditions of Tetany Mature animals are far more susceptible to grass tetany than younger ones because of their inability to mobilize Mg from their bones to meet the need for homeostatis in the body fluids. The slow depletion of plasma Mg and Ca probably precludes the occurrence of tetany in younger animals. Tetany has been seen in younger animals, but rarely. Tetany usually occurs near parturition or until approximately 2 months postpartum, and the frequency usually increases with older cows. Young animals and steers rarely get tetany.
Tetany occurs most frequently in beef cows grazing pastures.
Cool, rainy weather generally accelerates the occurrence of this malady. Pastures heavily fertilized with high levels of nitrogen or pastures with high soil K are more likely to produce tetany-prone pastures, but tetany will occur under other conditions also. Although tetany is caused by a metabolic deficiency of Mg and Ca, usually it is not possible to prevent it with supplemental Mg and Ca in mineral mixes. These minerals, especially Mg, need to be supplied almost on a daily basis, and the consumption or mineral mixes by all animals is usually not consistent enough to prevent tetany in a herd of animals, although it will help. This problem is accentuated in large pastures.