Haemorrhagic septicaemia, an imrortant bacterial disease of dairy animals (buffaloes and cattle), results due to infection of Pasteurella inultocida. Undoubtedly improved managemental practices and regular vaccination program has significantly contributed to lowering the incidence of the disease in our country, however, the pattern of the diseases has under gone changes and contrary to the past, presently the outbreaks are mostly experienced in young animals, especially, calves. The latter are invariably left unvaccinated thinking that they are safe by virtue of their passive immunity.

The present project was designed to have an idea regarding the actual period for which maternally derived antibodies were able to afford protection against any possible attack of the infection. The study was conducted on fifty pregnant, randomly selected buffaloes, maintained at livestock production and research institute Bahadarnagar Okara (LPRI).

The serum samples of the vaccinated mothers were collected a month before parturition. The serum samples of the calves were collected once before taking colostrum then at the interval of two weeks for the first four weeks. All subsequent sampling was done at an interval of four weeks. The processing of the samples for antibody titre was carried out through ELISA and haemagglutination tests.

The indirect haemgglutination and enzyme linked immunosorbent assay tests showed that the titres of maternally derived antibodies, received by taking colostrum, attained a peak during the first two weeks and gradually decreased in the following two weeks i,e up to the age of one month. At the age of 8 weeks calves were found with 0 titres.

Aanalysis of IHA revealed that the IHA titres of calves rose from 1.932 GMT to 6.824 GMT from birth to 2 weeks of age and gradually faded to 6.714 GMT after four weeks of age. calves were found with 0 titres at the age of 8 weeks.

The analysis of ELISA titres showed highest antibody titre (36.225 GMT) was in calf on 2nd week and then declined (32.633 BMT) gradually upto 4th week. At the age of 8th week calves were found with titres (4.366 GMT) almost negligible.

Buffalo dams (407.) were found with low titres when examined for their antibody level 30+10 days before parturition, despite the fact that they received vaccination according to the normal schedule of the farm.

Results of the study indicated that there was great need for improvement of vaccine and vaccine schedule i,e animals should be immunized thrice a year. Pregnant dams should be vaccinated late in gestation period so as to raise their antibody levels against the disease, ensuring a sound passive immunity of their off springs. Calves should also be regularly tested for their maternal antibodies and should be immediately vaccinated if passive protection is over. The funding of the present study necessitate the vaccination of calves at 2 months of their age.