Keep cow magnesium levels up

Managing Magnesium Levels in Cattle

Low magnesium levels in cows can lead to serious problems at the worst possible time. As calving approaches, the demands on the animal’s body are already high. A deficiency in magnesium can cause grass staggers, a sharp drop in milk production, or even sudden death. These are the kinds of losses that can hit hard on a lifestyle block, both emotionally and financially.

Why magnesium deficiency is hard to fix quickly

Magnesium acts a bit like a battery in the body. You cannot top it up overnight. Once levels are low, they take time to recover. The real challenge is that even if you start supplementing, it may not be enough to restore normal levels in time.

Cows that have grazed short pastures or poor-quality feed over summer are particularly vulnerable. Their magnesium intake will have been limited for weeks or even months. By the time symptoms show, the whole herd may be at risk.

Blood testing provides an early warning

One of the best ways to understand what is going on in your herd is to ask your vet to take a few blood samples. These can be analysed quickly by a lab to check magnesium levels. You only need to test around 10 percent of your cows to get a good picture. Avoid including heifers, as their mineral requirements and metabolism are different.

Your vet will help interpret the results and advise whether any emergency measures are needed. If blood levels are already below normal, supplements alone may not be enough to turn things around without additional support.

Prevention is better than cure

Testing does more than just give you a number. It can highlight other potential mineral imbalances or deficiencies that may be brewing below the surface. You might not like the results, but having the information puts you in control. It gives you a chance to act before you start losing animals.

If you are unsure about your cows’ mineral status or you’ve had issues with grass staggers in the past, take the time to talk to your vet and get those tests done. It is a small investment that can make a big difference.

If you are new to cattle or just want a refresher on the practicalities of keeping them healthy, our What You Need to Know to Keep Cattle course covers all the essentials, including nutrition, health checks, and seasonal risks.