February 2012
Feeding Facts

As Spring Approaches It’s Time to Consider Grass Tetany

As our attention turns to spring and the anticipation of spring grass or late-winter grazing of a winter annual, we as cattle producers need to be aware of the potential problem of grass tetany from North Alabama into the Florida Panhandle. The potential for grass tetany (grass staggers) is always a concern for cattle producers in the spring. The cause of grass tetany is cattle being unable to intake sufficient amounts of magnesium.

Cows are most vulnerable when grazing lush, green forages either low in magnesium and/or high in potassium. High levels of potassium will interfere with magnesium absorption by the animal. Therefore, pastures fertilized with products like potash, chicken litter and ammonium sulfate will only increase the chance of grass tetany.

Grass tetany generally occurs in late-winter or early-spring in cows shortly after giving birth. Cows are more susceptible to grass tetany on cloudy overcast days as compared to sunny days. At the onset of tetany, animals will appear nervous, and muscles can be seen twitching. As the condition progresses, animals will have problems walking, will eventually go down and will normally lie on one side and thrash about. If the condition is not corrected, death may occur within three hours.

Since nothing can be done to control the weather, the best alternative to prevent grass tetany is to feed a complete mineral or supplement tub with adequate levels of magnesium. These products should be provided at least 28 days prior to when cattle are most susceptible to grass tetany and should be provided throughout the time grass tetany is a concern. Cattle require 10 grams of magnesium per head per day as a prevention to grass tetany. Most high magnesium minerals will contain 14 percent magnesium for grass tetany prevention, while most high magnesium supplement tubs will be at least 4 percent magnesium. Each product will provide at least 10 grams per head per day due to different intake levels.

Magnesium is very unpalatable, so you should only provide high magnesium minerals to cows 30 days prior to through grass tetany season. During the other times of the year, you should provide a complete mineral containing at least 2 percent magnesium, along with at least 5 percent phosphorous for good reproductive and immune response performance. Your local Quality Co-op will carry Formax® Minerals, Sweetlix® minerals as well as STIMU-LYX® Supplement Tubs to meet the magnesium requirements of your cattle at this time.

If you have an acute case of grass tetany, a sterile solution containing magnesium and calcium is given intravenously to the cow. This must be done slowly to prevent rapid increases in blood calcium levels which can cause heart failure. In most cases, cows will respond rapidly to this solution treatment. In some cases, you may deal with a chronic cow that will have to be treated more than once to completely recover.

The best way to stop grass tetany is to prevent it. To accomplish this, provide a high magnesium mineral to cattle at least 28 days prior to grazing lush, green forages. Make sure the mineral is provided to cattle at all times and they are consuming an average of at least three ounces of mineral per head per day.

Your local Co-op can assist you in providing the right products and equipment to help in any area of cattle production. If you have any questions concerning grass tetany or other mineral concerns, please contact your local Co-op or e-mail me at This email address is being protected from spambots. You need JavaScript enabled to view it..

Jimmy Hughes is AFC’s animal nutritionist. He looks forward to hearing from you or visiting with you in the future.