Grass tetany, also known as ‘hypomagnesemia’, is a potentially fatal metabolic disorder in cattle caused by low levels of magnesium in the blood. It often occurs in lactating cows grazing on lush, rapidly growing pastures, especially in the weeks between Spring and Summer. However, there are many other factors including severe weather or stress that can also cause grass tetany. Recognizing the signs early and providing prompt treatment is crucial to prevent fatalities.
Here are the key signs and treatment methods for grass tetany:
Signs of Grass Tetany:
Early Signs:
Restlessness and Irritability: The cow may exhibit unusual nervousness or be more excitable than normal.
Muscle Twitching: Look for twitching in the muscles, especially around the face and ears.
Unsteady on Feet: The cow may stagger or show difficulty walking.
Moderate Signs:
Lack of coordination: The cow may have difficulty standing or appear to stumble frequently.
Reduced Appetite: Decreased interest in food, leading to reduced intake.
Frequent Urination and Defecation: More frequent than normal.
Decreased Milk Production: A sudden drop in milk yield.
Severe Signs:
Convulsions: The cow may experience violent muscle contractions and seizures.
Coma: If untreated, the cow may slip into a coma.
Death: Rapid progression from early signs to death can occur within hours.
Treatment & Prevention of Grass Tetany:
Administer Magnesium:
Intravenous Magnesium: The most effective treatment is the immediate administration of magnesium sulphate intravenously, usually combined with calcium to prevent concurrent hypocalcaemia.
Subcutaneous Magnesium (under skin): In less severe cases, or following IV administration, magnesium can be given subcutaneously. All IV treatments should be carried out by the veterinary surgeon
Immediate Veterinary Care if symptoms are severe.
Oral Supplements as Part of a Regular Diet:
Magnesium Supplements: Provide magnesium supplements in the feed or water. This can help increase blood magnesium levels over time and prevent recurrence.
High-Magnesium Mineral Blocks: Ensure cattle have access to high-magnesium mineral blocks or licks.
Environmental and Dietary Management:
Avoid High-Risk Pastures: Limit access to lush, rapidly growing pastures, particularly in early spring. Gradually introduce cattle to these pastures to allow their metabolism to adjust.
Supplement with Hay: Provide dry forage like hay, which can help reduce the risk of magnesium deficiency.
Balanced Diet: Ensure the diet is balanced with adequate levels of magnesium, calcium, and other essential minerals.
Monitoring and Prevention:
Regular Monitoring: Closely monitor cattle for early signs of grass tetany, especially during high-risk periods.
Preventive Supplements: During high-risk periods, routinely provide magnesium supplements to lactating cows and those in late pregnancy.
Grass tetany requires prompt recognition and treatment. If you suspect a cow has grass tetany, contact your vet immediately. Implementing preventive measures, such as providing magnesium supplements such as mag flakes in water troughs and managing pasture access, can significantly reduce the risk of this condition. Regular monitoring and early intervention are key to protecting the health and productivity of your herd.