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Lactation tetany, Grass Tetany, Grass Staggers, and Wheat pasture poisoning are synonyms for hypomagnesemia.

It is mainly related to nerves. There is nervous disorder of cattle which is due to low level of Magnesium. Animal would be excited, there is muscle spasm and death may occur and most commonly occurs as complex entity e.g. acidosis. Normal value of magnesium is 1.8-3 mg/ 100 ml of blood. Affected animal has 0.9 mg/100 ml.


  • Chances of this are more common in beef animal as compared to dairy animals because animal fed on high protein diet will have more conversion into ammonia. This high production of ammonia may stop the absorption of magnesium from rumen. So animals on proteinaceous diet are more prone to magnesium deficiency.

  • In a study it was observed that 88 % cases of hypocalcemia also having hypomagnesemia in lactating animals.

  • Other causes may be renal insufficiency.

  • Excessive potassium can shift magnesium level sharply and can shift to nervous signs and even death. Hyperkelemia can also lead to heart failure.

  • If fed on high lush green Pasteur. Leguminous plants like lucern are rich in magnesium but avoid giving because they also contain saponin and cause blot.

  • In estrus there is low Mg because demand of Mg increases.

  • If deficiency of spdoi, salts in ration, potassium level increases and magnesium level decreases.

  • Secretion of magnesium in milk is also the cause of low magnesium level. Cow producing 20 litres of milk is 3 times deficient in magnesium than cow in dry period. Lactating cow should be given magnesium supplement.

  • Fasting cows also have magnesium deficiency

  • There are two types of hypomagnesemia:

  • It could be hypomagnesemia along with hypocalcemia. Signs are tetany, stiffness of neck and legs.

  • It could be hypomagnesemia with normal Ca level. It is acute and rarely happens. Sudden convulsions and death occurs.

  • Old animals are more prone to magnesium deficiency

Signs and Symptoms:

  • staggering gait

  • Stiffness of fore limbs

  • Grinding teeth

  • Neck muscle tremors are common signs

  • Convulsions

  • Collapse

  • Death may occur

  • In most cases cow suddenly collapse and no clinical signs

  • Two forms in dairy animals:

  • Peracute Lactation Tetany:
    Animal is off feed, tends to be more alert due to excitability and twitching of muscles and ear followed by uneasiness, bellowing, champing of jaws and salivation, temperature could be 107.6 oF, and more audible heart sounds. There is increased heart rate. Animal died if untreated.

  • Sub Acute Lactation Tetany:
    Less severe signs: off feed with low milk production, staggering gait, stiffness of neck muscles, twitching, pupil dilated, and grinding of teeth.

Differential Diagnosis:

  • Lead poisoning: it does not respond to magnesium therapy.

  • Ketosis: ketone bodies in blood

  • Tetanus: more stiff and prolapse of third eye lid.

  • Nitrate poisoning: urine color is of coffee color.


  • 30 g of MgSO4 in 300 ml of water. Care should be taken that it causes bradycardia and may lead to heart arrest. It can be given through intravascularly but safer if given through subcutaneously.

  • If complex situation, Calcium and magnesium deficiency. Calcium borogluconate 60 g along with 30 g of MgSO4.

  • Magnesium licks: MgO 35.7 % in molasses which lowers incidence.

Give hay right after parturition. Epsom salt 3-6 g/liter of water may be given. Carbohydrate supplements can also be given in the form of molasses particularly animal going toward calving and peak production; this will dilute the protein level. Similarly young calves fed on milk upto 3 months (all milk diet) may have deficiency of Mg. These sorts of calves are apparently blind, there is convulsions and death may occur. So give 10 g of Mg SO4 in 100 ml through subcutaneously route and shift all milk diet with concentrate and add 5 g of MgSO4. This will lower the incidence of magnesium deficiency.