Tackling Grass Tetany on Irish Dairy Farms

grass tetany magnesium

April 10, 2020

Why are Dairy Cows prone to Grass Tetany and how to best tackle it?

Farmers across Ireland are facing an unusual Spring season as a Dairy Farmer. In this blog, we look at ‘Grass Tetany’ and how to best prepare your dairy herd.

What is grass tetany/staggers?

Hypomagnesemia is the technical term and it is characterised by a subnormal level of magnesium in the blood. It is generally associated with grazing.

Typical symptoms are reduced milk yield (up to 15% loss of production), nervousness and muscular tremors.

In the acute form, the cow staggers around, froths at the mouth, collapses and dies.

Research shows that cows are known to have low stores of magnesium in their bodies.  Getting an adequate amount of minerals is shown to have a positive effect on reducing Grass Tetany. While it’s evident that cows have magnesium in their bones, they can only mobilise this very slowly.

Cows are typically poor at absorbing magnesium in their guts. This means they require daily intakes of magnesium. Lactating animals during this season have an increased requirement for magnesium also. Anything that affects the gut function or DMI dry matter intake can disrupt magnesium absorption.

minerals for tackling grass tetany

What Are the Risks Involved?

  • Certain swards will be poorer at taking up or storing magnesium. Clover swards are better at taking magnesium, while lush ryegrass swards can be poorer.
  • Fertilizer applications can affect uptake. Potassium will lock up magnesium and also nitrogen fertilizers will lead to more ammonia in the rumen which may affect magnesium uptake.
  • Anything that affects DMI (dry matter intakes) can disrupt daily intakes of magnesium. So adverse weather can play a role where we need to be extra vigilant when the weather changes in spring.
  • Stress causes a redistribution of magnesium in the cow’s body increasing the risk. This can also be seen in suckler cows sometimes in autumn time at weaning due also to lower DMI at this time.
  • Spring grass can be lower in fibre and high in oils (fats like CLA) which can lead to increased gut transit times and potentially lower absorption rates of magnesium. These all make grass tetany high risk during spring grazing.

What are the Causes of Grass Tetany?

The main causes of Grass Tetany are:

  •  Magnesium deficiency
  •  Poor feeding intake
  •  Cold and wet weather
  •  Animal stress at weaning
  •  High potash applications

What Treatment is available for tackling Grass Tetany?

It is always cheaper to prevent than to cure. The recommended solutions are:

  • The administration of magnesium sulphate intravenous
  • The use of intravenous calcium borogluconate
  • Having a well-wilted silage to slow down the digestion process and increased magnesium from diet.
  •  Adding magnesium compounds in the drinking water supply

It is recommended that a vet should be called immediately to administer small volumes of intravenous mentioned above as deemed fit. For a full list of approved Vets in Ireland, CLICK HERE.

How to Prevent Grass Tetany? 

We know cows need daily intakes and the spring season poses some increased risks. We need to ensure magnesium supplementation during this key risk period.

magnesium dairy cows

Supplementing Dairy Cows:

  • Magnesium can be given through water. This is the most effective way of ensuring adequate mineral intake specifically suited to the needs of your herd. It is cost-effective and reduces the intensity of labour requirements. 
  • Mg in concentrates being added to feed – but be careful to allow for this when reducing meal in the diet.
  •  Magnesium boluses are an option that can be used but they only cover for 3 weeks.
  • Palatable licks and high magnesium buckets.
  • We can feed fibre in the diet during the spring to reduce the risk from lush spring grass high in oils and low in fibre. Most care should be taken when lush low covers are being grazed in particular.
  • Pasture dusting magnesium can be done also but is very labour intensive.

What have the Terra NutriTECH Farmers had to say?

One less job to do and I have healthier cows that hold condition after calving.

Source: Independent IFAC Report

Very little milk fever and grass tetany.

Source: Independent IFAC Report

“Removing activities such as giving nutrient boluses and dusting minerals on silage.”

Source: Independent IFAC Report

Please call Ronan on 087 7086714  to find out about using an automated mineral dosing system. There are many health benefits for your cattle. Continue planning for the year ahead.