Grass tetany in beef cattle: prevention and treatment

 Grass tetany in beef cattle: prevention and treatment

Grass tetany, also known as “grass staggers”, “wheat pasture poisoning”  “winter tetany”,

Hypomagnesia

Introduction

is a fatal metabolic disease caused by low levels of magnesium in the blood serum of ruminant livestock including beef cattle,  dairy cattle and sheep.
Grass tetany primarily affects mature cows nursing calves two months or younger, but can also occur in young cows and growing calves. It happens most frequently when cattle are grazing succulent, immature grass and often affects the best cows in the herd.

What causes grass tetany?

High nitrogen fertilization reduces magnesium availability, especially on soils high in potassium or aluminium.  Grass tetany occurs most frequently in the spring, often following a cool period (temperatures between 45 and 60°F) when the grass is growing rapidly, but also is seen in the fall with new growth of cool-season grass or wheat pastures.

Contributing causes are:

magnesium levels are lower in cool-season grasses and cereals than in legumes or weeds. 

levels are low in grasses grown on leached acid sandy soils levels are low when potash and nitrogen fertilisers are used and growth is vigorous.

high moisture content in grass causing rapid gut transit and low uptake.

reduced absorption of magnesium resulting from high rumen potassium and nitrogen and low rumen sodium

low energy intake, fasting or sudden changes in feed

bad weather, especially winter storms

stress such as transport or yarding

low roughage intake (young grasses have low roughage and often poor palatability)

low intake of phosphorus and salt.

What are the signs of grass tetany?

Typical signs of grass tetany begin with an uncoordinated gait and terminate with convulsions, excitability with muscle twitching, an exaggerated awareness and a stiff gait. Animals may appear aggressive and may progress through galloping, bellowing and then
coma, and death

Prevention and Control

Management should aim to eliminate factors that reduce magnesium absorption and provide a magnesium supplement.

Treatment of affected animals

Blood magnesium levels must be restored. Veterinary administration of an intravenous calcium and magnesium solution produces the best results. However, in acute cases where time is critical, producers can inject a calcium and magnesium solution under the skin.

Producers should also provide oral sources of magnesium to affected herds to prevent relapses.

These include:

magnesium oxide powder for dusting onto feed or pasture

magnesium lick blocks

slow-release capsules

magnesium sulphate or soluble magnesium chloride added to hay or silage

adding magnesium to concentrates or pellets.