Causes of death in calves with experimentally induced bovine neonatal pancytopenia (BNP).

: The objective of this study was to identify the different causes of death in calves affected with bovine neonatal pancytopenia (BNP). A total of 51 precolostral calves were fed with colostrum from cows which had lost at least one calf after parturition due to BNP in previous lactations. Clinical BNP could be induced in 71% (36/51) and subclinical BNP in 20% (10/51) of the calves. 9% (5/51) of the calves stayed BNP-unaffected despite challenging with the same mixed colostrum and approved passive transfer of colostral antibodies. The case fatality rate in BNP-affected cases was 83% (38/46). In the 38 lethal BNP-cases gross-pathological and histopathological examinations were performed. BNP-induced haemorrhagic anaemia was the cause of death in 18 calves (47%). 19 of these lethal cases (50%) died due to infectious diseases, especially due to pneumonia, enteritis and septicaemia. One calf died due to severe enteritis and exsiccosis without any signs of BNP (3%). In conclusion, anaemia as the consequence of haemorrhages was the most prevalent cause of death in BNP-affected calves, however, BNP has been approved to increase the lethality of common infectious neonatal diseases.