Low Magnesium – Grass Staggers
July 2024

Low magnesium grass staggers, also known as hypomagnesemia, is a common issue affecting cattle in New Zealand, especially in regions with lush pastures. This condition arises when cows experience a deficiency of magnesium in their system, leading to various neurological symptoms. Magnesium (Mg) is an essential element in the body and is required for helping maintain normal calcium levels, muscle and nerve transmission, energy/protein metabolism and much more. Cows cannot strip Mg from their bones like they can with calcium in times of deficit, they must get it through their diet on a regular basis.

For numerous reasons, July/August/September is a common time for this condition. Cold wet soils below 12˚C reduce the uptake of Mg by the plant. Short, lush rapidly growing pasture will naturally contain less Mg. In the first few days after calving cows will have a reduced intake resulting in not being able to eat enough to meet nutrient requirements which can be complicated with milk fever and sub-clinical ketosis. Lactation can play a factor as higher producing cows will be at more of a risk.

Clinical signs of low Mg grass staggers in cows can vary but often include:

  • Muscle tremors + staggering gait
  • Loud pounding + increased heart rate
  • Tooth grinding + irritability/aggression
  • Seizures/paddling
  • Sudden death

When it comes to treatment, early detection is crucial. If a cow is displaying symptoms of Mg deficiency, prompt intervention is necessary to prevent further complications. Veterinary assistance should be sought to confirm the diagnosis and provide appropriate treatment. Treatment often involves administering Mg therapy and many cases require calcium as well.

Prevention plays a key role in managing this condition. One effective method is to provide magnesium supplementation through feed additives or mineral supplements. This ensures that the cows receive an adequate amount of magnesium in their diet to meet their nutritional requirements. Blood sampling cows pre-calving is a useful tool for monitoring Mg levels to ensure changes to supplementation are made early.

In addition to supplementation, consider the grazing risks – changing a cow’s diet from saved pasture to the 2nd round (fresh short regrowth, especially if quantity is limited) is often a big trigger for magnesium-based issues and supplementation over this period can be a cheap insurance. Monitoring the magnesium levels in soil and forage can also assist in identifying areas where supplementation may be necessary.

In conclusion, low magnesium grass staggers is a significant concern for cattle in New Zealand, particularly in regions with lush pastures. By implementing proper management practices such as magnesium supplementation, rotational grazing, and balanced nutrition, you can effectively prevent and manage this condition in your herd. Early detection, timely treatment, and proactive prevention strategies are essential in ensuring the health and well-being of cows affected by low magnesium grass staggers.