The application of immune serum is one of the most efficient method used formerly in the protection of raised piglets’/weaners’ health . The objective of the study was to determine specific antibody response during hyperimmunization of fatteners with a self-prepared subunit vaccine, and to propose production method of immune serum against Gram-negative bacteria antigens. The vaccine was administered every two weeks, 4 times. Individual and pooled serum samples were assayed for IgM, IgG and IgA antibodies against Histophilus somni recombinant Hsp60, H.somni rOMP40 and Pasteurella multocida LPS. Additionally total serum IgG and haptoglobin concentrations were measured. Two weeks after the first vaccination IgM antibody raised significantly against H.s. rOMP40 and LPS, whereas after 4 weeks it increased against rHsp60 antigens. Anti-LPS IgM antibody raised up stepwise till the end of the observation, but IgM antibody against H.s. rHsp60 and H.s. rOMP40 decreased in further samplings. A significant raise in IgG class H.s. rHsp60- -antibody was found 4 weeks after the first immunization and a similar raise against two remain- ing antigens after 6 weeks. The intensity of the reaction increased till the end of the experiment. The raise in IgA antibody level was observed only for H.s. rHsp60 antigen. Clinically observed, proper animal health and welfare were confirmed by haptoglobin concentration, which remained in physiological range. At least 4 booster doses were necessary to obtain hyperimmune serum containing a high level of antibodies against examined antigens. The number of immunizations influenced response profiles for specific IgM, IgG, IgA antibodies.