August 2011 Articles

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Don't Let Tetany Be a Problem For You This Year

Don't Let Tetany Be a Problem For You This Year
Source: Jeremy Powell, U of A Once cool-season forages begin to reemerge in your grazing pastures, grass tetany can become a potential problem. This disease normally occurs in Arkansas in the months of February, March and April and is due to an abnormally low level of magnesium in the cow's body. Early signs of tetany include decreased appetite, decreased milk production, frequent urination, separation from the herd, increased excitability as well as a stiff or unsteady gait. These early signs may occur for as little as two to three hours, making early detection difficult. As the disease progresses, an affected cow will lose normal muscle control. This forces the affected animal to lie down, and they may become unable to get up. They will usually exhibit muscle tremors and spasms. If your cattle are not checked often, a dead cow can commonly be the first sign of a problem. The cause of this disease is associated with the fact that cattle and other ruminant animals absorb magnesium from the intestinal tract much less efficiently than other species. Furthermore, magnesium (Mg) can become low due to losses in the milk of a lactating cow or due to an increase in the cow's potassium intake. High potassium levels occur in young, rapidly growing forage and can be a problem in cool-season grasses such as fescue or in winter annual cereal grains like wheat and oats. High potassium levels directly interfere with the cow's digestive ability to absorb magnesium. Many other factors can be associated with the onset of this disease: Weather can play a role in grass tetany. It is usually cloudy, misty and/or cold when this disease occurs. These weather conditions decrease the plant's ability to utilize magnesium, making it even less available to the grazing animals. Other stressors on the cattle such as hauling, penning or heavy lactation can also promote the disease. Grass tetany most commonly occurs in mature, lactating cows and typically affects cows that are slightly over-conditioned and would likely be referred to the "best" cows in the herd. However, it can also affect cows with a very poor body condition score that are excessively thin. Younger animals in the herd rarely have problems with this disease. - 2

Spring fertilizer application can exacerbate problems with grass tetany. High potassium levels in the forage due to heavy fertilization of grazing pastures with potassium (pot ash) can in turn inhibit magnesium absorption in a cow's intestinal system. All these conditions can potentially occur at the same time in late winter and early spring, leading to problems with grass tetany during that time of the year. Prevention is the key to controlling grass tetany. This can be achieved by dispending a salt-mineral supplement containing at least 10 percent Mg that can be utilized daily by animals grazing tetany-associated pastures. Follow these suggestions.
Provide 2 ounces of Mg oxide supplementation per animal per day. It must be provided on a daily basis because the cow's body has no ability to store up reserves. Several mineral feeders should be made available if stocking rates are higher for the herd. Review fertilization practices in order to not make this disease more prevalent. Fertilization should be based on recent soil samples taken from the farm. Alternatively, grazing young animals on high-risk pastures can be another method of controlling this disease.
Contact your county Extension office for more information about grass tetany and other cattle management recommendations