GRASS TETANY

  • Highly fatal disease of all classes of ruminants.
  • Highest incidence in lactating cows.
  • Synonyms: Lactation Tetany, Milk Tetany, Transit Tetany, Winter Tetany
  • Dietary deficiency along with nutritional or metabolic factors reducing the availability of Mg.

Characterised by:

  • Hypomagnesemia
  • Hypocalcemia
  • Tonic clonic muscular spasms
  • Convulsion and death due to respiratory failure

Etiology

  • Deficiency of Mg in the blood.
  • Impaired mobilisation & absorption of Mg from bone & gut respectively.
  • Loss of Mg in milk (0.12g/lt).
  • Feeding lush pasture grasses.
  • Heavy application of K & N rich fertilizers.
  • Low carbohydrate content diet.
  • Scour/diarrhoea.
  • Feeding of cereal pasture mainly wheat.
  • Transportation stress (release of epinephrine and decreased serum Mg level)

Clinical signs

Acute Tetany

  • Sudden cease of grazing
  • Unusual alertness
  • Twitching of muscles and ear
  • Hyperaesthesia with slight disturbance
  • Continuous bellowing
  • Frenzied galloping
  • Gait becomes staggering
  • The animal falls with obvious tetany of the limbs, which is rapidly followed by clonic convulsions lasting for about a minute.

Sub-acute Tetany

  • The onset is gradual.
  • For over a period of 3-4 days, there is slight inappetence, exaggerated limb movements.
  • The cow often resists being driven and throws her head about as though expecting a blow.
  • Spasmodic urination and frequent defecation are characteristics.
  • The appetite and milk yield are diminished and ruminal movements decrease.
  • Muscle tremor and mild tetany of the hind legs
  • Straddling gait and trismus.
  • Sudden movement, noise, the application of restraint or insertion of a needle may precipitate a violent convulsion.

Chronic Tetany

  • It occurs in animals which recover from the subacute form of the disease.
  • Low serum Mg levels but do not show clinical signs.
  • Dullness, unthriftiness and indifferent appetite.
  • In lactating cows, there may be the development of paresis and a milk fever-like syndrome that is poorly responsive to calcium treatment.
  • Depressed milkproduction.

Differential diagnosis

  • Acute lead poisoning.
  • Rabies
  • Nervous ketosis
  • Bovine Spongiform Encephalopathy
  • Poisoning by Clavicepspurpurea
  • Strychnine poisoning
  • Avitaminosis A

Treatment

  • Administration of preparations with Mg or Mg and Ca IV (Mifex 1 bottle or ½ bottle followed by 100-150ml of 10% MgSO4).
  • Chloral hydrate (IV) to reduce the severity of convulsions during treatment with magnesium.
  • Combined Ca-Mg therapy (e.g. 500 mL of a soln. containing 25% Calcium borogluconate and 5% Magnesium hypophosphite for cattle,50 mL for sheep) lV.
  • S/C injection of 50% magnesium sulphate(200 ml for Cattle and 20 ml for Sheep)
  • Mg therapy:-200-300 mL of a 20% solution of Mg sulfate injected IV protects for 3 to 6 hours.
  • 200 ml of 50% MgSO4 weekly for two times sub cutaneously
  • 3 % of Mg Lactate IV or SC gives prolong protection.
  • 15% of Mg gluconate @200-400 ml IV is more ideal with prolong protection.
  • Rectal infusion of 100 ml of 30% MgCl in severe cases achievesnormal serum Mg level in 10 minute Mgadepate 12% along with Ca-gluconate also used.