The best practicable condition for the dipping process was heating at 58-60°Cfor 2 minutes. No contamination occurred in the defeathering process when 100 ppm chlorine water was jet for 1 minute. Contaminants were destroyed in the cooling process when the carcase was dipped in water containing 100 ppm chlorine at 5°Cor lower for 20 minutes. Moreover, it was necessary to wash the carcase with 100 ppm chlorine water before and after the removal of rectal contents following defeathering and the eviscerating process in order to make the final product free from contamination.
The immunological response was compared between chickens 3 weeks of age immunized with killed Newcastle disease virus (NDV) and then exposed naturally to infectious bursal disease (IBD) and Marek's disease (MD) viruses and unexposed control chickens free from IBD and MD. Agar gel-precipitating (AGP) antibody against IBD was detected in all the chickens 2 weeks after exposure, and the antibody against MD in 3 of 7 chickens 6 weeks and in 4 of 6 chickens 7 weeks after exposure. The control chickens were negative for IBD and MD antibodies over a 7-week experimental period. A difference in immunological response to NDV assayed by hemagglutination-inhibition (HI) and serum neutralization tests was found between the exposed and control chickens. The mean antibody titer was significantly lower in the former than in the latter. When challenged with virulent NDV, All the control chickens were protected, but only 2 of 7 exp bsed chickens survived and responded with higher HI titers 2 week after challenge. These findings indicate that young chickens vaccinated with killed NDV and subsequently exposed to IBD and MD had depressed antibody production and protection against challenge with virulent NDV.
Lyophilized bovine viral diarrhea (BVD) live virus vaccine was prepared tentatively from attenuated BVD virus cultured in ST cells. Neutralizing antibody produced after vaccination decreased hardly in titer even after one year. When vaccinated at 1-9 months of pregnancy, 12 cows gave birth to normal young. Vaccinated cattle induced no contact infection. No accident was observed among about 1, 500 cattle inoculated in the field. Antibody response was seen in 99.1%. No decrease in infective titer occurred in the vaccine stored at 4°Cfor 18 months, or in the thawed vaccine stored for 2 days.