Enzootic bovine leucosis seropositivity in milk powder-fed calves

In an otherwise enzootic bovine leucosis (EBL) free herd the authors found seropositive calves. It has been demonstrated with experiments that seoposi tivity of the calves was the result of supplementation of the maternal colo strum with milk powder made from colostrum and feeding it to the calves on their second and third day of life. Milk powder made from the milk of EEL-i nfected herds was positive with the ELISA test. Thus it is concluded that t he anti-EEL antibodies that remained intact during powderisation got, absor bed by the calves, and this passive humoral immunity was detected in the ca lves' sera with ELISA. Seropositivity in the four examined animals persiste d for 38-63 days after drinking the supplemented milk. Further investigatio ns are needed to find out whether milk powder made From an infected animals ' milk can be a source of infection and if this is a real threat to the fre e status of EEL-free herds.