Video 13 Watch out for grass tetany

Grass tetany or hypomagnesia is what is classed as a true veterinary emergency. With this deficiency every passing minute is critical. These animals will have low blood magnesium which means quick intervention is a matter of life or death.

Magnesium plays a key role in nerve function and it often the most important muscle in the body that can eventually fail, the heart.

The symptoms

With classic grass tetany or staggers, we will see the cow down trashing and convulsing. Often they will be grinding their teeth, legs and head can be flailing wildly. Their heart rate can be rapid and loud.

With up to 30% mortality in grass tetany being reported we must act fast. Every farm should have 2 bottles of magnesium sulphate in the drugs cabinet.

Ring your vet and safely administer 1 warmed bottle of magnesium sulphate under the skin to give you time. Great care should be taken doing this, aproach the cow on the opposite side to the legs flailing.

Some cows may also rarely show subclinical symptoms. These animals will be standing and confused. They can go off their milk suddenly and be similar to cases of nervous ketosis or meningitis. They can also be highly unpredictable in my experience. So seek your vet’s advice to confirm a diagnosis.

The treatment of grass tetany will involve subcutaneous magnesium sulphate and intravenous calcium borogluconte. Your vet may have to sedate these cases and make the choice around small volumes of magnesium administered intravenously. This can only be done by careful clinical experience and careful monitoring of the heart rate.

Why are cattle prone to grass tetany

Cows have low stores of magnesium in their bodies. While they have magnesium in their bones they can only mobilise this very slowly.

Cattle are often poor at absorbing magnesium in their guts. This means they require daily intakes of magnesium. Lactating animals have an increased requirement for magnesium also.

Anything that affects the gut function or DMI dry matter intake can disrupt magnesium absorption.

The risks

• Certain swards will be poorer at taking up or storing magnesium. Clover swards are better at uptaking 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 n the cow’s body increasing the risk. This can 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.

Prevention

We know cows need daily intakes and the spring poses some increased risks.

We need to ensure magnesium supplementation during this key risk period.

We can supplement using

• Mg in concentrates being fed but be careful when reducing meal in the diet that you allow for this
• Magnesium boluses but they only cover for 3 weeks
• Palatable licks and high magnesium buckets
• Magnesium can be given through water
• 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. The 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,

For the details on how we can tackle hypomagnesemia or grass tetany watch the video above

Thought for the day

In hard times the human spirit will often require to be resilient. Resilience is about overcoming the unexpected and  also helps in the belief that the sun will keep rising and things will get better

Huge thanks to Nettex and Rumenco in helping support me in making this series for more information click the link here https://www.rumenco.co.uk/products/dairy/grass-staggers

Happy safe farming