Various test conditions were examined to establish the complement fixation (CF) test procedures of chicken sera for practical application. From the experiment in which fresh duck, goose, and pigeon sera were tested for their cofactor (avian C′1) activity that is essential for CF reaction of avian antibody, duck serum was proved to be most suitable as cofactor. Thus, standard CF procedure was established by employing a given amount of fresh duck serum in the reaction system, and was shown to have higher reproducibility and to be more practical than the other methods previously reported. The procedure was successfully applied for detection of antibody to Newcastle disease virus in convalescent and hyperimmune chicken sera, and antibody to Mycoplasama galisepticum in convalescent chicken sera.
