Magnesium Deficiency – Grass Tetany

Posted September 28, 2016

Cattle store very little magnesium in their body and rely on a daily supply of magnesium in their feed. If pasture levels are low in this mineral, cattle can develop a magnesium deficiency.


Symptoms include:

  • Sudden death
  • Early signs - facial & ear twitching
  • Agitation towards sounds or movement e.g. being handled, birds flying overhead
  • Staggering - this manifests in severe cases
  • Lying on side with convulsions, muscle spasms, thrashing



A veterinarian will inject animals but if symptoms are recurring farmers may need to do so themselves, as once cattle go down they are very likely to die from the disease.



  • Pasture flush after good rains/spring pastures with low mineral content
  • Any reduction in feed intake e.g. restriction from pasture, being kept too long in the yards, bad weather preventing access to feed
  • Pastures fertilised with high nitrogen or potash
  • Lush winter pastures e.g. rye & oats.
  • Cows in early lactation



  • Riverina's Dairy Feeds contain extra magnesium for winter months, which works on most farms.
  • If an outbreak occurs, additional magnesium can be added to your dairy or beef feed.
  • Contact your Riverina sales representative or nutritionist for advice on feeding levels.
  • If your cattle are showing signs of magnesium deficiency, call your local veterinarian straight away.

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