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Grass tetany (lactation tetany or transport tetany) is caused by low levels of magnesium (Mg) in the animal. Low levels of magnesium cause decreased energy metabolism and other changes to normal body functions. Blood levels of magnesium should normally be 2.0-3.6 mg/dl.
Magnesium must be consumed in the diet. Wheat, cereal crop feeds, and some pastures are usually low in magnesium; therefore, animals grazing on these feeds may develop grass tetany. Magnesium is also lost in the milk. This is why some lactating animals may experience this problem. When animals consuming a low magnesium diet are stressed because of being moved or transported, tetany often results. Calcium levels also appear to play an important role in grass tetany.
Clinical Signs: In the early stages of disease, the animal may go off feed, be very alert, and excitable. The ears and muscles often tremble and the animal can be aggressive when stimulated. With time, the animal has a lack of coordination and may eventually collapse in seizure-like activity. If not treated properly, death can occur within hours.
Hypomagnesemia (grass tetany) is a nutritional disease. It is caused by feeding pasture plants grown in soils that are low in available magnesium and high in available potassium. It is most often seen when sheep are grazing cool season grasses or small grain pastures or rapidly growing lush grasses in the spring or fall. Clinical signs are sheep walking with a stiff gait, loss of appetite and avoidance of the rest of the flock. They are nervous, have staring eyes, twitching skin and may also stagger. Treatment can be successful if given early with 50 mL of a saturated solution of magnesium sulfate injected I.V. or rectally. Grass tetany can be prevented by feeding high magnesium mineral salt mixtures.
Penn State University's Department of Veterinary Science
This page was last updated on: February 15, 2008