April 2015
Farm & Field

Get Tough on Grass Tetany

  Spring quick growth and high nitrogen levels can increase chances of grass tetany making it vital to keep cattle supplied with magnesium and calcium levels.

It’s April, and you’re watching the cattle graze all that lush, new growth. All the applied nitrogen and quick growth are paying off as you listen to the herd ripping off and chewing grass in unison. Beneath that peaceful, pastoral scene, there may be a problem waiting to explode.

When grass is growing fast early in the growing season, cattle may not be willing to eat enough dry matter to meet all their nutritional needs. Cattle may love eating all the fast-growing forage, but they can be left with a magnesium and calcium deficiency.

Grass Tetany

According to the Department of Animal Sciences at Purdue University, grass tetany is a metabolic disorder of cattle related to a deficiency of magnesium. Also known as grass staggers or hypomagnesaemia, grass tetany can occur in fall and winter, but it’s most common in spring when cattle are grazing thick, quick-growth pastures made up of orchardgrass, perennial ryegrass, timothy, tall fescue, wheat, Kentucky Bluegrass, annual ryegrass and small grain grasses.

You may be thinking, "That’s all the grass I have growing in my pasture." Well, this time of year, the majority of beef producers are growing these grasses as well. The key is finding out if there is a magnesium deficiency in your grasses. Purdue recommends doing soil tests to determine any magnesium and calcium deficiencies and completing a forage analysis.

Southland Veterinary Services owner Phillip H. Wilson has successfully treated many cases of grass tetany, but says preventing the disease is cheaper than treating it.  

Purdue University completed studies showing that the risk of grass tetany decreases on pastures containing over 30 percent legumes. This would include clovers, alfalfa, birdsfoot trefoil or animals that have wintered on grass-legume hay. Not only will legumes add natural forms of nitrogen to the soil, they can also help prevent grass tetany if they are growing in conjunction with pasture grass.


Phillip H. Wilson, DVM, owner of Southland Veterinary Services and veterinarian for over 20 years, says cool, damp weather increases the risk of grass tetany in cattle.

"When a cow gets grass tetany, you will see her show various symptoms such as goose stepping, running, agitation, or the cow may be completely down and you will see where the animal has been paddling around trying to get up," Wilson said. "Unfortunately, when most producers realize a cow has grass tetany, she may already be dead, but you want to take steps to make sure the rest of the herd is protected."

Even though the culprit is a lack of magnesium, Wilson says calcium is just as important.

"When the magnesium level in the cow goes down, it will drive the calcium level down as well," Wilson explained. "The calcium drives all muscle function including skeletal, smooth and cardiovascular muscles."

  Any cattleman can administer the gel, foreground, to the cow orally if she is down. The gel is available at most livestock supply stores. However, a vet should administer the IV to an infected cow because it is necessary to continually monitor the cow for signs of heart failure if the calcium levels have dropped too low.


Wilson said a cow that is down can be given a calcium paste orally.

"Once I squirt the paste into the mouth, I will then administer an intravenous calcium and magnesium solution," Wilson said. "When I treat a cow, I give the first treatment by mouth, then an IV with a mixture of calcium, magnesium, potassium and phosphorous. If she can handle the IV, I then administer more solution by injecting it into the stomach."

The paste can be administered by any cattle producer and is available through most livestock supply stores.

"A veterinarian needs to administer the intravenous injections since there can be a danger of heart failure if this solution is given too rapidly," Wilson warned.

Wilson said the cow should be getting two ounces of magnesium per day to help prevent grass tetany.

If grass tetany is becoming a problem for the whole herd, Wilson gives advice.

"You should remove the cows from the feed source, feed them with hay supplemented with grain and provide the trace mineral mix until all threat of grass tetany is gone," Wilson stated. "It usually takes around two weeks to get the herd back to a healthy situation."


Many pastures are fertilized with poultry litter or commercial fertilizer, and this can result in grasses having higher nitrogen and potassium levels. Keeping a free-choice mineral containing 8-12 percent magnesium and 16 percent calcium throughout the year helps prevent grass tetany. Providing the herd with magnesium and calcium through a high-quality trace mineral mix from your local Quality Co-op can give that extra insurance that your cows are safe from grass tetany.

"The good thing about magnesium and calcium when mixed with trace mineral salt is salt is an intake limiter, and cows won’t overdose on the important nutrients," Wilson said. "It provides an ongoing supply of the important minerals they need."

This April, before you enjoy the fun watching your cattle graze on lush, spring forages, first, take a look to see if your mineral tub is full of quality Co-op mineral supplement. The qualified professional at your Co-op will be able to provide a mix right for your cattle.

John Howle is a freelance writer from Heflin.