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cowwHypomagnesaemia (or grass staggers) in cows:
  • Hypomagnesaemia is relatively common in cows in heavy lactation and on lush pasture (inadequate energy intake and low magnesium content).
  • Basically the underlying cause is low magnesium intake, but low body condition, changeable bad weather, yarding and transportation all predispose.
  • Another contributing factor is the autumn/late winter application of nitrogen and potassium, which can interfere with magnesium absorption in the animal’s digestive system.
  • Often the only sign is sudden death.
  • Sometimes signs develop before death - increased nervousness, body tremor, walking with stiff legs, collapse with paddling and the head held back.
  • In dairy cows it’s common for a mild form of the condition to develop. The only signs are lowered milk production, weight loss and increased nervousness, which may make the cow seem ‘difficult’ to milk.
  • It’s not unusual for affected cows to be extremely aggressive - so take care!
Hypomagnesaemia in ewes
  • Hypomagnesaemia causes occasional deaths in lactating ewes on lush pasture, although it can occur in dry sheep as well.
  • It sometimes causes dramatic signs such as body tremor, walking with stiff legs, collapse with paddling and the head held back.
  • Usually ewes are just found dead, on their sides with scuff marks in the ground where they have been kicking.
  • The early signs can be subtle, with an increase in nervousness that can be easily overlooked or misinterpreted. The nervousness can lead to mismothering lambs.
  • Blood tests, which can be arranged by your vet, will tell when blood concentrations are getting low.
  • Urgent treatment is vital for cows and ewes.
  • Treatment means injection of magnesium solutions, preferably by a veterinarian.
  • In cows and ewes, prevention includes providing shelter from bad weather, and dusting pasture or hay with magnesium oxide powder or calcined magnesite.
  • Dusted pasture may not be very palatable, and if the powder is applied too liberally the stock may go hungry to avoid it. This can precipitate acetonaemia.
  • Wear a mask when applying the dust.
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