Bovine Hypomagnesemic Tetany Study Guide

Overview and Clinical Importance

Hypomagnesemic tetany (commonly known as grass tetany, grass staggers, lactation tetany, or wheat pasture poisoning) is an acute, often fatal metabolic disorder of ruminants characterized by hypomagnesemia (low serum magnesium) and associated neurological signs including hyperexcitability, muscular spasms, convulsions, and death. This condition is one of the most important metabolic emergencies in bovine practice and represents a high-yield topic for the NAVLE examination.

The disease primarily affects lactating beef and dairy cattle grazing lush, rapidly growing pastures in spring and fall. Understanding the pathophysiology of magnesium metabolism, recognizing clinical signs, and implementing appropriate treatment and prevention strategies are essential competencies for veterinarians working with cattle.

Etiology and Pathophysiology

Magnesium Homeostasis in Cattle

Magnesium (Mg) is the fourth most abundant cation in the body and the second most abundant intracellular ion. It is essential for numerous enzymatic reactions including ATPases, kinases, and phosphatases, as well as normal nerve conduction, muscle contraction, and bone mineral formation. Approximately 60-70% of total body magnesium is bound in bones, but this pool is not readily mobilizable in adult cattle.