2.5.2. Preparation of antigen for ELISA
The antigen for ELISA was prepared by disrupting the pure culture of P. multocida (P52 strain) using 100-Watt ultrasonic disintegrator at 6 amplitude peak to peak for 30 min (Almeida et al., 1979). Concentration of the protein of sonicated antigen was adjusted to 1 g/5 L as measured by the method of Lowry et al. (1951).