The correlation between the proportion of reactor lactating cows and the presence of antibodies to the bovine viral diarrhoea virus (BVD) in bulk tank milk was studied by using the ELISA test. Serum and individual milk samples from 376 unvaccinated lactating cows from 10 herds located in the South region of the State of Minas Gerais and the Northeast region of the State of São Paulo as well as one milk sample from the bulk tank milk of each herd were analysed. Reacting serum samples were found in all the herds, and this occurrence varied from 12.28 to 100.00%. The analysis of individual milk samples did not show reacting cows in two herds, while the other herds had an ocurrence varying from 5.26 to 70.83%. Antibodies were detected in bulk tank milk from herds whose proportion of reacting sera was equal to or higher than 82.86%, and whose proportion of reacting individual milk samples was equal to or higher than 32.14%.
Bovine viral diarrhoea; Antibodies; Milk; Serum; ELISA
