EN
The aim of the study was to isolate the most common pathogenic strains from calves, cows and the environment, as well as estimating the intensity of (OD) of IgG₁, IgG₂ and IgM reactions to those microorganisms. The study was held in a large commercial dairy farm over the course of 1 year, and included 100 calves and their mothers. OD of IgG₁, IgG₂ and IgM to bacteria isolated from cows, calves and the environment were examined in the investigated serums using the ELISA test. Higher levels of OD were obtained in relation to Salmonella Dublin, Pasteurella multocida, Escherichia coli O26 K6 and Haemophilus som. The above bacteria were also considered to be the most dangerous microorganisms for young calves in the studied farm.