Grass Tetany
Tetany season winds down in spring; providing cattle magnesium helps.
The risk of grass or winter tetany is lessening as spring approaches, but it is not totally out of the picture for beef cows, according to Eldon Cole, a livestock specialist with University of Missouri (MU) Extension.
Tetany is a metabolic condition that results from low magnesium intake in older, heavy-milking cows. Symptoms in the affected cows show up as nervousness or marked changes in attitude (like a normally gentle cow acting aggressive and ultimately going into paddling convulsions). Death can occur if intravenous treatment is not given promptly.
Tetany is a complex condition that involves soil, plant, animal and weather interaction. It is most often noted in cool, damp, stressful weather with the cows grazing lush smallgrain or cool-season grass pastures. It may occur earlier in the winter when grass hay is being fed.
“Some years seem much worse than others for tetany outbreaks. So far, this winter very few reports of tetany have been made,” Cole says.
Even though low magnesium levels in the forage or soil are blamed for tetany, phosphorus and potassium imbalances play a part in it.
Tetany risks are reduced as soil temperatures rise and cold, stressful weather disappears. The conditions usually occur in mid-April.
“The best advice to farmers who wish to keep their guard up if they have high-risk cows is to provide a supplement that contains magnesium,” Cole says.
Magnesium is not a mineral that can be stored in the animal, so daily intakes in a mineral or concentrate supplement offer the best preventative help. The degree of risk can guide supplement purchases.
Mineral supplements that have a 2- to 4-ounce (oz.) daily intake should have around a 10% to 12% magnesium level on the tag. This should provide adequate protection for most situations.
“The high-risk cows, those over 6 years of age near calving or with 6-week-old calves, may need their magnesium blended in with a palatable concentrate feed. In this case the target intake is 1 to 2 ounces of magnesium oxide per day. Fall-calving cows typically do not present a tetany risk,” Cole said.
For more information get the University of Missouri Guide Sheet, “G4669 — Mineral Supplements” at the nearest MU Extension Center or online at www.extension.missouri.edu.
For more information, contact any of the MU Extension livestock specialists in southwest Missouri: Eldon Cole in Mount Vernon, 417-466-3102; Gary Naylor in Dallas County, 417-345-7551; and Dona Goede in Cedar County, 417-276-3313.
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