As the days shorten and a new flush of growth appears in our fields, it’s easy to think the grazing season is winding down. However, for many UK livestock farmers, autumn brings a heightened risk of a serious and often fatal condition: grass staggers. Also known as hypomagnesaemia or grass tetany, this magnesium deficiency can strike cattle and ewes without warning, making it crucial to be prepared.

Grass Staggers, also known as Grass Tetany, is a metabolic disorder caused by critically low levels of magnesium in an animal's blood. Magnesium is vital for proper nerve and muscle function, and because the body can’t store it effectively, a continuous supply is needed from the diet. When this supply drops, a cascade of neurological symptoms can occur, leading to a state of hyperexcitability. Magnesium can't be stored in a cow's body, so they need a continuous supply from their diet.

While grass staggers can happen at any time of year, autumn is  one of the  peak-risk periods for several reasons:

• Lush Grass: Following summer droughts, autumn rainfall can trigger a flush of new, leafy grass. While this looks great, it is often low in magnesium and high in potassium and nitrogen. These high levels of potassium and nitrogen interfere with the cow's ability to absorb the limited magnesium that is present.
• Weather Conditions: Cold, wet, or frosty weather can put stress on animals, increasing their magnesium requirements.
• Lactation: The risk is particularly high in lactating cows, as a significant amount of magnesium is lost in milk.
• Many pastures will have received slurry and farm yard manure, which can increase the risk

The signs of a magnesium deficiency in cows can be subtle and often appear when it's already too late. Because of this, prevention is essential. However, if you are vigilant, you can spot earlier symptoms:

• Early Signs: Increased nervousness, twitching of the ears and muscles, and a stiff, uncoordinated gait. The animal might appear to be "staggering" (hence the name "grass staggers").
• Advanced Signs: In severe cases, the animal may go down, showing convulsions, muscle spasms, and thrashing. This can quickly lead to death.

Managing grass tetany is all about proactive prevention, not reactive treatment.

Supplement with Magnesium: This is the most effective strategy. Options include:

• Supplement sheep with Hi Mag rolls
• High-Magnesium Mineral Licks or Blocks: Simple and effective for free-access supplementation.
• Magnesium Boluses: Long-lasting and a good option for ensuring every animal gets a dose.
•  Magnesium in Feed or Water: Can be mixed into a feed ration or added to the water supply.

Offer a Balanced Diet: Providing access to hay or silage alongside grazing can help. The fibre content slows down digestion, improving magnesium absorption.

Soil Management: Be mindful of potash (potassium) fertiliser application in grazing pastures, as high levels can further compound the problem.

By understanding the risks and taking a few simple preventative steps, you can help protect your herd or flock and ensure a healthy and productive autumn season.
For further advice, visit your nearest Wynnstay store or speak to your farm rep.

Read more: How to prevent grass tetany using a magnesium supplement

By understanding the risks and taking a few simple preventative steps, you can help protect your herd and ensure a healthy and productive autumn season.