Even farmers who have taken measures to get magnesium into their suckler cows should be staying vigilant at present. The fact is that no one measure will be 100% certain to prevent the condition.

On Monday morning, a cow was found dead in the field at Tullamore Farm – a suspected grass tetany case. The animal in question had direct access to water-borne magnesium.

This is not the first case of grass tetany at Tullamore Farm in 2017 and despite efforts made to prevent the condition, a ‘perfect storm’ of external factors has heightened our risk:

  • Weather: the obvious one. As well as stressing the animals, wet weather is reducing grass and water intakes. The cows are now getting less energy in and visiting the drinker – our main magnesium source – less frequently.
  • Leafy grass: cows are grazing covers of 8-10cm, which are exceptionally high in leaf content. This material will be rapidly digestible, lower in dry matter given the weather, and run through cows very quickly. The increased passage rate can reduce the rate of nutrient absorption in the digestive system.
  • Cow type: 80% of Tullamore cows are first-cross and still working themselves hard to produce large amounts of milk – a stressor in itself.
  • Reseeding: the majority of the farm was reseeded this year and the animal in question was grazing a reseeded paddock. The slurry, dung and compound fertilisers that are important in reseeding will have brought up the ground’s potassium (K) concentrations. The uptake of magnesium is negatively affected by K.
  • What now?

    We will now look to introduce additional tetany-prevention measures on Tullamore farm:

  • Introduce mineral lick buckets (note, not all animals will visit these).
  • Look to move animals to stemmier covers during inclement weather, if possible.
  • Move in with fibrous forage, like hay or straw, to slow the rates of digestion in cows.
  • Avoid paddocks that have received significant slurry/K applications.
  • Consider administering magnesium boluses.
  • Avoid pushing animals to graze out paddocks during unsettled weather conditions.
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