Grass Tetany (Hypomagnesaemia) in Cattle & Buffalo

Grass tetany (hypomagnesaemia) is a sudden, life-threatening drop in blood magnesium that makes cattle and buffalo stagger, twitch, go down and convulse, often within hours of being moved onto lush, fast-growing green fodder. It is a true emergency: untreated animals can die the same day, so call a veterinarian immediately for intravenous magnesium. Day-to-day prevention rests on steady magnesium and mineral supply, especially during the flush of green fodder after the monsoon.

What is grass tetany?

Magnesium controls how nerves and muscles fire. Lush, rapidly growing grass and cereal fodder are often low in available magnesium and high in potassium and nitrogen, which block magnesium absorption from the gut. Because the body stores very little magnesium, levels can crash within a day of a feed change, especially in high-yielding and freshly calved animals that lose magnesium in milk.

Signs to watch for

• Nervousness, flaring ears, a stiff or staggering gait
• Muscle twitching over the face and flank, teeth grinding
• Going down, paddling the legs, convulsions
• Sudden death with no warning in the most severe cases

Emergency first aid

Grass tetany kills fast. Keep the animal calm and quiet, avoid startling it (noise and handling can trigger fatal convulsions), and call your veterinarian at once. Treatment is intravenous or under-the-skin magnesium given by a vet; do not attempt IV injections yourself, as a wrong rate can stop the heart. This is an emergency that needs professional help, not a wait-and-watch problem.

Which animals are most at risk?

• High-yielding dairy cows and buffaloes in early lactation
• Animals moved suddenly onto young, heavily fertilised green fodder
• Older cows, which absorb magnesium less efficiently
• Herds fed little dry fodder alongside lush grazing

Prevention: keep magnesium and minerals steady

• Introduce lush green fodder gradually and always offer dry fodder or hay alongside it to slow passage and aid absorption
• Provide a balanced daily mineral mixture so magnesium and other minerals never run short
• Pay special attention around calving and in peak lactation, when losses are highest
• Avoid sudden feed changes and overgrazing of young regrowth after rain

A consistent daily mineral mixture is the single most reliable safeguard. Cattle Remedies Verymin supplies a balanced blend of macro and trace minerals to keep high-yielders topped up through the green-fodder season, and Calcicril supports calcium and mineral balance around calving, when tetany and milk fever risks overlap. To choose the right product for your herd, see our best mineral mixture for cattle in India guide. Because staggering and going down can also signal milk fever or wider mineral deficiency, a quick vet assessment is important. If lush fodder is also causing bloat, review our green-fodder bloat guide.

Frequently asked questions

How fast does grass tetany kill?

It can be fatal within a few hours of the first signs. Any staggering, twitching or collapse after a feed change should be treated as an emergency and a veterinarian called immediately.

Is grass tetany the same as milk fever?

No. Milk fever is low calcium and grass tetany is low magnesium, but both cause a down, weak or convulsing cow around calving, and they can occur together. Only a vet can tell them apart and give the correct intravenous treatment.

How can I prevent it during the green-fodder season?

Feed dry fodder alongside lush grass, introduce new fodder gradually, and supply a balanced mineral mixture every day so magnesium never drops, paying extra attention to freshly calved and high-yielding animals.

Important note

This article is general guidance for Indian dairy and livestock farmers and is not a substitute for veterinary diagnosis. Grass tetany is a medical emergency; always consult a qualified veterinarian. References: ICAR; Merck Veterinary Manual (hypomagnesaemic tetany); U.S. National Library of Medicine (PubMed/PMC). By Cattle Remedies.