Data are recorded concerning the phosphorus partition of the blood of cattle grazing over phosphorus deficient pasture of the Union of South Africa. The outstanding characteristic is low inorganic phosphorus, with a correlated reduction in total phosphorus.

When a small ration of bone meal is given to the cattle, comparatively normal figures are shown. Heifers approaching two years in age, supplied with bone meal from weaning onwards, show a normal inorganic P fraction of 5 mg. per 100 c.c. of blood. Control heifers without bone meal show 2·3 mg., or less than half. Control cows may drop to 1 mg., or even lower. Calves of control mothers are normal so long as milk supply is adequate, but may show reduced inorganic P if aphosphorosis of the mother is acute. In general, low inorganic P in the blood is associated, with poor condition of the animal. Rapid colorimetric determination of inorganic P in the blood of the grazing animal, easily obtained from the jugular vein, provides a simple means of detecting phosphorus deficiency in the pasture.

Although long-continued phosphorus deficiency leads to the clinically recognisable disease “Styfsiekte,” especially in lactating animals, the less pronounced deficiency, manifested as malnutrition and stunting of growth, without direct mortality, is detected by blood analysis with equal certainty.