Grass Staggers

Farm vet Pablo provides more information on Grass Staggers; what it is, what causes it, how to prevent it and treatment. Read more here…

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The seasonal topic of this month is Grass staggers, a metabolic disease caused by magnesium (Mg) deficiency. It is also called hypomagnesaemia.

Magnesium (Mg)

Mg plays an important role in nerve and muscle function and functioning of the immune system. Although cows have significant stores of Mg in the bones, only a little of these stores are available to maintain levels in the blood. Therefore, the cow is dependent on the Mg supplied in the diet and from supplements to maintain blood levels. Blood and urine tests can confirm Mg deficiency.


The initial symptoms of Mg deficiency are nervousness, twitchiness, muscle tremors, staggering, ears pricked, nostrils flaring, eyes alert
and head held high. Cows suffer loss of appetite and reduced milk production. Movement is stiff, like a cow is walking on stilts, and she will stagger when forced to move quickly. This progresses rapidly to the cow going down and suffering seizures and convulsive ‘paddling’. Death results from a “tetany”, where the muscles contract uncontrollably, including the heart.


grass staggers

Staggers is typically seen in unsupplemented grazing cows (beef or dairy) at the peak of lactation following spring turnout in wet weather, or in the autumn when there’s a late flush of grass. Grass staggers can be prevented, it is recommended that dry cows receive a diet containing 0.35 percent Mg, and lactating cows 0.28 percent Mg.


There are several sources of magnesium, and different methods of adding these into a cow’s diet. Common methods include drenching, pasture dusting, as magnesium bolus, and through water (treat all water sources, or cattle might avoid the supplemented water and drink elsewhere). Each method has its own limitations and advantages, so it is up to each farm how they choose to supplement their magnesium.

Factors that increase Mg requirements of cows during the winter/spring period are:

  • Diets naturally low in Mg and/or high in potassium (K) e.g. pastures (low Mg or high K), maize silage or fodder beet (low Mg), paddocks with high potash or effluent (high K).
  • Cold wet weather in spring, depressing grass growth cow intakes.
  • High cow demand for Mg over calving and early lactation, e.g. due to high milk production.


Call us as soon as you suspect Grass staggers. The treatment is Mg under the skin, plus some calcium given slowly into the jugular vein. Staggers is an emergency – the sooner we arrive the better the prognosis will be.

If you have any questions about this give us a call and we will be more than happy to help you.

Out of hours emergency

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