Beware of grass tetany risks over the coming weeks

The focus at farm level, for farmers who have not already done so, is switching to turnout and getting animals out to pasture. But farmers need to be acutely aware of the risks associated with grass tetany.

Grass tetany is caused by a Magnesium deficiency which can occur when animals are grazing rapidly-growing, lush, low-fibre pasture – especially where heavy nitrogen has been applied.

Suckler and dairy cows are at risk of developing grass tetany. This is especially the case on pastures rich in Potassium and Nitrogen.

These pastures may have received artificial or slurry applications earlier this spring.

The risk of the metabolic disorder occurring is also heightened during periods of cold and wet weather or during periods when animals come under stress.

Such stress factors include cows coming bulling or a rapid change in diet, such as switching from a silage-based indoor diet to a grass-only diet post-turnout.

Identifying grass tetany

The symptoms of grass tetany or ‘staggers’ include frothing at the mouth, staggering, severe tremors and visual distress.

In cases where treatment is not carried out, there is a good chance that the animal will succumb to a rapid death.

In situations where the disorder has been identified the most appropriate action is to call your veterinarian to have the animal treated. Treatment often involves the administration of Magnesium Sulphate.

Reducing the risk of grass tetany

Farmers can employ a number of practices to reduce the risk of grass tetany occurring on their farms.

These include pasture dusting, feeding a concentrate containing Magnesium, offering cattle licks or blocks or supplementing Magnesium through the water system on farm.

However, it must be noted that the intakes from licks or blocks are variable and some cows will intake more or less than their requirement of 30-40g of Magnesium.

The use of a buffer feed, such as straw or hay, may also be used to reduce the risk of grass tetany occurring.

The addition of straw or hay to the diet slows down the digestion process of lush green grass through the rumen, thus allowing the animal to absorb more Magnesium from the diet.

Methods to reduce grass tetany:

  • Feeding high Mg (Magnesium) concentrates.
  • Adding Mg to water troughs.
  • Feed hay or straw as a buffer.
  • Avoid grazing pastures with high amounts of slurry and/or Nitrogen applied.
  • Dusting pasture with Mg.
  • Mineral licks.
  • Magnesium boluses.