§ Sir A. Baldwinasked the Minister of Agriculture, Fisheries and Food if he is aware of the increasing concern about hypomagnesaemia in cattle; and what advice he will give to farmers about the nature, prevention and treatment of this disease.
§ Mr. John HareYes. A recent survey suggests that about 1 per cent. of dairy cattle are affected by the disease; it is also frequent in non-lactating and beef cattle and occurs at all ages.
Work on this problem has been going on at my Central Veterinary Laboratory and elsewhere for some years. The condition is associated with a fall in blood magnesium levels, but it has not yet been positively determined what causes this to happen. Clinical symptoms vary with the intensity of the attack and may include nervousness, restlessness, loss of appetite, twiching of muscles, especially in the face and eyes, grinding of the teeth, contraction of tail muscles, staggering and paralysis, and often the animal dies unless treatment is started in good time. Since some of these symptoms occur in other diseases, a veterinary surgeon should be called in as soon as suggestive symptoms are observed so as to ensure that an accurate diagnosis is made.
Hypomagnesaemia has been found in cattle on pastures with a relatively high magnesium content. It cannot, therefore, be attributed solely to magnesium deficiency in the accepted nutritional sense, although oral supplements of magnesium will in most cases prevent a fall in blood magnesium to dangerously low levels. 176W Two ounces of calcined magnesite for adult stock, with smaller amounts for younger cattle, have been used successfully as a preventive during periods when individual experience suggests that hypomagnesaemia is likely to occur. It is essential that each animal should consume this dose daily; heavy dosing before turning out does not prevent the disease.
Experimental work and field studies have shown that, under favourable circumstances, a very good measure of control can be achieved by top-dressing with magnesium compounds. The amounts necessary vary considerably according to local conditions, e.g. the calcium status of the soil, husbandry procedures, and weather, and if preventive measures of this sort are contemplated expert advice should be sought. Further research is required before treatment of pastures can be recommended generally as a fully effective and economic alternative to oral dosing.