EN
Calves aged 2 to 4 weeks were examined for the presence of antibodies against parainfluenza-3 (PI-3) virus, infectious bovine rhinotracheitis/infectious pustular vulvovaiginitis (IBR/IPV) virus, virus diarrhoea-mucosal disease (VDMD) and adenovirus. The obtained results showed that PI-3 antibody levei in calves was higher in winter season (October-April) than in summer (May-September). Similar differences were found also among relative number of animals reacting positively. Antibodies against PI-3 and IBR viruses were found in 76.0 and 28.7 per cent of animals, respectively. No antibodies were found against adeno and VDMD viruses. The effect of possible activating action of meteorological factors on the course of parainfluenza-3 in calves was discussed.