Hypomagnesaemia (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.