Treat, Prevent Hypomagnesaemia (Grass Tetany) in Beef Cattle

ISU Extension and Outreach publication on common, preventable cattle disease


AMES, Iowa – Hypomagnesaemia (grass tetany) is caused by low magnesium in the blood, and most commonly found in older, lactating cows feeding on lush spring grass. Producers should monitor their herds for signs of tetany, be ready to treat it and work to minimize the causes of the disease, according to a new Iowa State University Extension and Outreach publication titled “Treatment and Prevention of Hypomagnesaemia (Grass Tetany) in Beef Cattle.”

Before physical signs are obvious, cows may have a grass tetany in beef cattledecrease in milk production and udder edema. Physical signs of grass tetany include irritability, twitching, incoordination, staggering, collapse and paddling. Cases left untreated will lead to coma and death. However, prevention can be accomplished by delaying turnout until grass is taller than six inches and supplementing magnesium in the diet.

This publication is authored by Grant Dewell, associate professor in beef production and extension beef veterinarian, and Steve Ensley, senior clinician and veterinary toxicologist. It can be accessed online at the ISU Extension and Outreach Store.

“Grass tetany is a recurring problem for spring calving cow herds and loss of a cow during early lactation is costly and leads to orphan calves,” Dewell said. “Proper care of pastures beforehand and careful attention to cows is critical to prevent death loss.”

This new publication will help producers identify signs of hypomagnesaemia in order to initiate treatment quickly, and provides advice on monitoring forages and magnesium supplements.