Grass Tetany: Treatment and Prevention

  1. Fairfarmhand
    When cattle are first grazing on the lush, green grasses of spring, lactating, mature cows are at a higher risk for grass tetany. Grass tetany is a metabolic disorder that is caused by a magnesium deficiency. The symptoms of the acute form of grass tetany are spasms, a cow lying on her side with her neck kinked back, and the animal is unable to get up. She will paddle her legs uselessly while lying down. The cow may be quiet between convulsions, but any form of stimulation, like the farmer touching her, will bring on another spasm.


    An animal with acute grass tetany does not have long left to live if she is left untreated. From the onset of symptoms, it may be only four to eight hours before the cow dies. A cow in the throes grass tetany needs swift action if she is to live.

    First, all handling of the animal must be done quietly and gently. Over-excitement will bring on more spasms, which can result in her death. If you do not have access to veterinary care, you can create a solution of 50 percent magnesium sulfate (Epsom salts) and water. Mix together 100 ccs of water and 100 ccs of Epsom salt and inject it underneath the skin. This can buy you some time until you can get the proper treatments. This solution should calm the animal enough to allow you to administer other medicines without stressing her.

    Next, you can give the cow an intravenous treatment of magnesium. Some ranchers and vets use a calcium-magnesium gluconate solution. If you are not experienced with such things, call the vet promptly to administer this treatment. IV treatments that are given too fast or at the wrong temperature can kill the cow.


    Cattle that have had one brush with grass tetany are more likely to have another in the same season. To prevent a relapse and to keep your other cattle from developing the same symptoms, you should supplement your cattle with magnesium.

    You can mix magnesium in with the cattle feed if you are feeding grain, or you can buy a high-magnesium salt and mineral block. Most lactating cows need from 13 to 15 milligrams of magnesium each day in their diets.

    If you've had one case of grass tetany, you should keep your eyes open for further cases. Look for symptoms of the sub-acute and chronic forms of grass tetany. The symptoms may be awkward gaits, twitching, loss of appetite, poor milk supplies, and sluggishness. If you see any of these symptoms, begin supplementation immediately.

    Don't take chances with the health of your herd. Many ranchers simply put out high magnesium mineral blocks when the grass begins to come in, just to stay on the safe side. This is the best precaution against grass tetany.

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