Now Is The High-Risk Time For Grass Staggers.

27th April 2022

After the long winter, it is good to see cattle grazing in the fields. However, there are reports of cow deaths due to grass staggers.

What is Grass Staggers?

Grass staggers, also known as Grass Tetany, is a condition caused by a low blood magnesium concentration. Vets may call this hypomagnesaemia, hypo (low) magnesaemia (blood magnesium).

What do cattle with grass staggers look like?

Cattle with grass staggers are often found dead, possibly with the soil around their feet disturbed due to paddling or seizures. If caught in time, affected cows may be twitching especially their head and ears, uncoordinated, staggering, nervous, collapsed and fitting.

It is important to keep cows with grass staggers calm as excitement can trigger a seizure.

What is the cause?

Although there is a store of magnesium in cattle bones, this is slow to enter the blood stream and essentially blood magnesium concentrations are dependent on daily dietary intakes. In the adult cow, most of the magnesium absorption occurs in the stomach (reticulum, rumen and omasum) with a small amount absorbed from the large intestine.

There are a few conditions in spring that make it a high-risk period for grass staggers

  • Cold and wet spring weather may disrupt grazing patterns and decrease intakes of grass and therefore magnesium.
  • Grazing in poor weather also increases stress levels, which decrease blood magnesium concentrations.
  • In spring, lush young pastures may be low in magnesium, or high in potassium and nitrogen which reduces the absorption of magnesium.
  • Lush pastures are also low in fibre, which increases the rate of passage through the stomach, reducing time for magnesium absorption.
  • Young grass, particularly those that fertilized with nitrogen, have a high fermentable protein content. This leads to an increased rumen ammonia concentration, which impairs magnesium absorption.


Rapid treatment is essential with an injectable solution of magnesium under the skin in the area behind the shoulder and over the ribs. The high magnesium solution should not be administered intravenously as this can cause fatal disruptions to heart rhythms. Your veterinary surgeon may administer a small amount of magnesium mixed into a calcium solution (and a sedative drug if needed) by slow intravenous injection while listening to the heart. This will only raise the blood magnesium for a short period, therefore it is essential to continue to supplement magnesium to grazing cows.


Providing some shelter from the wind and rain will help reduce stress and providing additional stemmy forages will slow rumen transit times, which increases magnesium absorption.

Cattle require 30 grams of magnesium daily. This can be provided through a few methods such as magnesium licks, water, boluses and compound feed.

Magnesium lick buckets are a particularly good method at providing magnesium, especially as they also supply additional energy which is essential for magnesium absorption.


In summary, grass staggers is a life threatening condition for grazing cows and now is the high risk time. High magnesium lick buckets are a particularly cost-effective method of offering cows a readily available source of magnesium.

For further information contact your local Fane Valley Store.