The experimental production of haemolytic disease of the newborn in calves.

Haemolytic disease in varying degrees of severity was produced experimentally in 15 newborn calves. Blood group antibodies, incompatible with some of the blood group factors of the calves, were produced in the dams of these calves by inoculation with non-parasitised red blood cells from the sire in most cases. These antibodies were absorbed by the calves from the colostrum. The resultant sensitisation of the calves' red cells produced acute intravascular haemolysis causing haemoglobinuria and anaemia. The principal factor governing the severity of the condition appeared to be the amount of sensitising antibody absorbed by the calf. The finding of leucopenia, thrombocytopenia, hypofibrinogenaemia, a reduction in plasma coagulation factors and the detection of fibrinogen degradation products indicated that disseminated intravascular coagulation occurs in this condition and is the cause of death in the acute cases where a haemorrhagic diathesis, fibrin deposition and oedema of the lungs are the main clinical and post mortem observations.