Grass Tetany in Ruminants - Frequently Asked Questions

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 What is grass tetany?
Grass tetany is a metabolic disease caused by a lower than average blood magnesium (Mg) level. It can affect all cattle and sheep but is usually seen in late pregnancy or within a month after lambing or calving when milk production is at its maximum. Grass tetany is most commonly seen in animals grazing lush spring pasture grasses.

What are the signs of grass tetany for cattle and sheep?
Often the first sign of grass tetany is a dead animal, or one that is dying in a convulsive, pedaling motion. Affected animals are often nervous or flighty, may appear uncoordinated, trembling or staggering.

Why does tetany affect animals newly turned out to graze pasture?
Unlike calcium, there is very little magnesium stored in the bones. Absorption of Mg is dependent on the Mg status of the animal, which is based on dietary intake. Magnesium needs to be supplied on a daily basis. Absorption of Mg is also influenced by the amount of calcium, phosphorus and potassium in the diet. Drought, heavily fertilized crops or pasture (with nitrogen and potassium or manure) and acidic soils all can reduce the absorption of magnesium in the animal’s system.

How can tetany be prevented?
Prevention of the disease is possible through ration supplementation. Livestock must receive adequate levels of calcium and magnesium through limestone and magnesium oxide. Consistent intake of mineral supplements on pasture can be difficult.

Is there a cure for tetany?
Treatment, if animals were found soon enough, would include injections of a combination of calcium and magnesium sulphate. Contact your veterinarian immediately.

For more information, see Tetany Problems in Beef Cows.

Prepared by Susan Markus, Ag-Info Centre, Alberta Agriculture and Rural Development

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This document is maintained by Mary Ann Nelson.
This information published to the web on May 27, 2003.
Last Reviewed/Revised on November 26, 2013.