Grass Tetany: Prevention and Treatment

Spring weather has finally arrived to many parts of the country. The snow (if you got any) has started to melt away and things are starting to grow again.

With the warmer weather and the winter moisture forage grasses have started their “spring Greenup”. It is during this time that forages come out of their dormant stage and begin growing rapidly again.

Though this may seem like the greatest time of the year, what with all of the green across the pasture, it is not without it’s own challenges. It is during this time of year a particular problem know as grass tetany can cause issues with your cowherd.

For those who are not in the know you may be asking “what is grass tetany?”, “what kind of problems can it cause in my operation?” and “How do I treat or even prevent it from happening?”. Well in regards to those questions here are some things that you should consider.

What causes grass tetany?

Grass tetany is a metabolic disorder that is caused by a low concentration of the mineral Magnesium in the blood. It can be found in all classes of cattle and if it is not treated in time it can be fatal.

This disease typically happens when cows graze rapidly growing lush, green pastures. It can occur when cows are grazing cereal grains but it tends to happen more often during the early spring with warm-season grasses.

During the early spring growth forages will be low in many minerals, including magnesium. It is during this time that forages don’t produce enough magnesium from the soil. This problem is compounded by the fact that since the forages are mostly water at this stage cows will not be able to consume enough of it to get the minerals that they will need.

The risk of grass tetany also increases in lush, green pastures that are high in Potassium and Nitrogen. Potassium and Nitrogen can interfere with the absorption of Magnesium by the cow.

The stage of production can also play a factor with the risk of getting grass tetany or not. Cows in the late gestation and lactation stages can get it because their body is using the Magnesium they consume for milk production.

Older cows tend to be more likely to get it vs their younger counterparts. This is because the older ones are not as able to pull Magnesium from place like their bones in order to meet their bodies demand for it.

   Symptoms

Diagnosing the symptoms of grass tetany just visually can be a little tricky. This is because the symptoms can come on so fast that by the time you can see them the cow could be already dead.

Some of the symptoms can be things like grazing away from the herd, increased irritability, muscle twitching, convulsions, decreased milk production, and even a staggered walk. Unless you are watching your herd very closely it can be difficult to see the early signs of grass tetany.

If left untreated cows will then lie down and begin a paddling motion with their legs. The final stages of the symptoms are that the cow will lay down, slip into a coma and then die.

Ways to treat it

Being able to treat grass tetany in a fast manner can be difficult because death of the cow can occur rather quickly, One day the cow may look fine but then the next she will be dead.

If your herd has been found to have grass tetany then the blood’s Magnesium levels will need to be restored immediately to prevent it from getting worse. There are a few different ways that you can go about doing that.

One way that this can be done is by a veterinarian giving an intravenous injection of a Magnesium and Calcium solution to the cow. This can work during the early stages of the disease when time is not as critical as later on.

If it is a serious problem and you need to act rather quickly then a producer can inject a Magnesium and Calcium solution under the skin.

There are also some oral options that are available to the producer. Though these options are generally to prevent any of your cows from relapsing. These oral sources of Magnesium are:

• A Magnesium oxide powder for putting onto either feed or on the pasture
• Magnesium lick blocks
• Slow-release capsules
• Magnesium sulphate or soluble magnesium chloride that can be added to hay or silage
• Adding magnesium to concentrates

These particular products can be purchased from your veterinarian or your local feed store.

Ways to prevent grass tetany

Because death can happen rather quickly preventing it from happening in the first place is really the best course of action to take. As they say “an ounce of prevention is better than a pound of cure”.

The general rule of thumb is to provide a mineral or lick tub with additional Calcium and Magnesium. You will want to go with one that has at least 8%-12% Magnesium. This will provide the minerals that your cows will need in addition to keeping grass tetany away.

If you would like to read more about the importance that minerals play in your cow’s diet then check out one of my previous posts “What you don’t know about minerals can hurt”.

Now onto when you should be putting the minerals out. According to the Veterinary Quarterly Review published by the Texas AgriLife extension service you should provide the supplement 30 days before grass tetany typically occurs. This usually means either in late winter or early spring.

During this time your forages are mostly water so increase the roughage and energy intake of your cows. Since your forages will be nearly 75% water any nutrients that they may provide will be watered down.

Another tactic you could go with is to reduce the level of Potassium and Nitrogen in your forages. Though these are also necessary nutrients too much of them can have a negative impact on Magnesium absorption. You can find out what these levels are by having your forages tested.