Speaking to a few farmers and vets this week, the recent wet and cold weather over the last few days seems to have brought a spike in tetany and pneumonia cases.

Suckler cows have a poor capability of storing magnesium (Mg) in their body and need a daily supply to prevent deficiency.

It is common with suckler cows when they are grazing very bare, as well as lush, pastures.

This grass is frequently low in Mg due to quick growth and heavy slurry spreading, which is high in potassium and can have a negative effect on Mg uptake.

It can be associated with stress such as transport, wet weather, cows in heat or changes in diet or pasture.

Cows under pressure sucking early spring-born heavy weanlings can also be prone to tetany.

Ways of controlling or preventing grass tetany include:

  • Feeding high-Mg concentrates.
  • The addition of Mg to the drinking water in the form of magnesium flakes (this can be questionable in periods of wet weather).
  • Buffer feeding with hay or straw.
  • Feeding 60g/head/day of cal-mag mixed through concentrates.
  • Giving free access to high-Mg minerals, either by way of powder mineral or mineral licks.
  • The use of magnesium bullets - at least two bullets/boluses should be used per cow, which will release Mg at a controlled rate each day for four to six weeks.

    Other advice for wet weather management

    Checking stock

    On a wet and windy morning, it can be tempting to do a count from the car window, but, in tough conditions, it’s really important to herd animals closely, especially younger animals. A change in temperatures can result in animals becoming sick quickly if there are other challenges.

    Small groups

    Group sizes should be kept smaller in wet conditions, as a smaller group will do less damage. On some farms, it may be possible to let cows out during the day and leave calves housed on straw. It will take away some housing pressure and mean calves have a warm, clean, dry bed.

    Young calves

    Keep a close eye on young spring calves. Make sure they are keeping up with their mothers when herding and make sure all calves are getting up and stretching. Try to graze cows with young calves in fields where there is lots of shelter until the current weather passes.


    If you have to rehouse, try to house on a dry day. Make sure young calves have access to creep areas. Be careful around low level drafts - I have heard of a few cases of pneumonia this week where calves where brought back indoors. Don’t stress cattle out for a few days when you rehouse. Leave any dehorning or vaccinating for a few days until cattle have settled again.