Whistlestop guide to grass staggers.

What is it - Hypomagnesaemia (grass staggers, grass tetany).

CAUSE - Lack of daily magnesium; Low magnesium in soil and grass; Lush pasture; High levels of potassium from fertilisers; High levels of ammonia (from nitrogenous fertilisers) inhibit magnesium absorption.

ECONOMIC IMPLICATIONS - Annual incidence of acute hypomagnesaemia around 0.5%; Many cows found dead.

MOST COMMONLY ENCOUNTERED IN - Older lactating beef cows 4-8 weeks after calving; Maintained at pasture; Without appropriate supplementary feeding; Often after stormy weather.

ACUTE DISEASE - Initial excitability; High head carriage; Twitching of muscles especially around the head; Inco-ordination (staggering gait); Startled expression; Teeth grinding; Rapid progression to seizure activity; Frothy salivation; Death may follow at any stage.

SUBCLINICAL/CHRONIC DISEASE - Cows may appear slightly nervous; Reluctant to be milked or herded; Depressed dry matter intake and poor milk yield; Dairy cows with subclinical hypomagnesaemia in the dry period are predisposed to hypocalcaemia.


SUDDEN DEATH - Lightning strike/electrocution; Anthrax; Clostridial disease.

ACUTE DISEASE - Lead poisoning; Hypocalcaemia; Nervous acetonaemia (dairy cow).

BLOOD DIAGNOSIS - Plasma magnesium less than 0.8mmol/l indicate subclinical hypomagnesaemia and an increased risk of developing acute hypomagnesaemia.

TREATMENT/PREVENTION - Veterinary treatment is essential; High-magnesium cobs; Supplementation with roughage such as straw; Shelter.