Changes in the amount of serum sialic acid in the vaccination of poultry against Newcastle disease

: A total of fifty birds of a four-line hybrid (Plymouth X Cornish) were used in an experiment to elucidate the link between the dynamics of serum sialic acid and the level of antihemagglutinins prior to and after vaccination against Newcastle disease (ND). It was found that immediately after vaccination the level of serum sialic acid rose essentially, and persisted at high values in the course of 7-8 days. It came back to the initial level at the time when the ND antihemagglutinins showed a maximum rise, i. e., when the active immunopoietic process was over. It is concluded that the changes in the serum sialic acid may be used tentatively as an adjunct in the evaluation of the immune responsiveness of the animal organism in the course of immunopoiesis following active immunization.