ON THE IMPORTANCE OF ANTIBODIES TO PASTEURELLA-HAEMOLYTICA A1 IN COLOSTRAL SERA OF COWS AND BLOOD SERA OF CALVES

Antibodies to P. haemolytica were detected in colostral sera of cows a nd blood sera of calves by means of indirect haemagglutination (IHA) a nd ELISA. The ELISA titres of the colostral sera of the dams and of th e blood sera of the calves showed a significantly positive correlation . There is a positive correlation between the titres of the two serolo gical methods. The results of the challenge infection with P. haemolyt ica A 1 do not show a correlation between the titres and the severenes s of the disease. Heifer calves, however, developed more severe pneumo nias than calves from older cows.