Fall in antibody titer to bovine leukemia virus in the periparturient period

Twenty-seven cows with antibodies to bovine leukemia virus were bled before, during and after calving. All serum samples were tested quantitatively for bovine leukemia virus antibodies using both the agar-gel immunodiffusion test with a glycoprotein antigen and the radioimmunoprecipitation assay with an internal p24 protein antigen. A significant fall (P less than 0.001) in bovine leukemia virus-antibody titer was demonstrated with both tests at the time of calving, with a subsequent rise in antibody titer within one month of parturition. Bovine leukemia virus antibodies were not detectable using the agar-gel immunodiffusion test in two of these cows at the time of calving.