Hypomagnesaemic tetany of calves

Young calves in the age group of 2-8 weeks and fed whole milk or milk replacer are more likely to develop hypomagnesaemia due to inadequate magnesium in diet. Magnesium concentration in milk is low, which may be adequate for growing calves upto a body weight of 50 kg. The intake of magnesium will be inadequate if the calves of higher body weight are fed solely on a whole milk diet. Chronic diarrhoea and chewing of bedding or course fibbers, that stimulate salivation, cause significant loss of magnesium in faeces and may exacerbate hypomagnesaemia in young calves.

The disease occurs sporadically and is clinically manifested by hyperexcitability, muscular spasms and convulsions. Initially, there is an increase in pulse rate, but as convulsions disappear the pulse becomes impalpable, and cyanosis develops before death. The condition must be differentiated from acute lead poisoning, enterotoxaemia caused by Clostridium perfringens type D, poleoencephalomalacia, tetanus, vitamin A deficiency, and strychnine poisoning. Normal serum magnesium level in calves ranges from 2.2 mg/dl to 2.7 mg/dl serum. A level below 0.8 mg/dl indicates severe hypomagnesaemia and the clinical signs appear at serum magnesium levels of 0.3-0.7 mg/dl. Calves are treated with 100ml of 10% solution of magnesium sulphate subcutaneously followed by dietary supplementation with magnesium oxide or magnesium carbonate (10 g once a day).