[Hog cholera: active immunity conferred by the Chinese strain vaccine to young pigs born to immune sows].
This paper deals with the comparative development of active immunity in young pigs which were born from unvaccinated sows and from recently vaccinated sows. The development of immunity is expressed by the neutralizing serum antibody titer and protection against a pathogenic virus. The results show that: --the post-vaccinal increase in antibodies is inversely proportional to the titer of passive antibodies at the time of vaccination, --protection at the end of economic life depends on the antibody titer at the time of the challenge, --young pigs born from a mother which is not immune can be vaccinated starting at the age of 7 days, --the percentage of protection at the end of economic life of vaccinated baby pigs with colostral antibodies ranges from 50% when the vaccination was carried out at the age of 7 days to 100% when the vaccination occurs at the age of 2 months.