Improvement of the inactivated oil-emulsion vaccine against AIV-H_9 subtype

Five-day-old and ten-day-old chicks were vaccinated with ND+H_5+H_9 inactivated oil-(emulsion) triple-vaccine made respectively from 6 AIV strains isolated in Guangdong and 1 vaccine strain now being used in practice.At the day vaccinated and post-vaccination till for sale serums of all chickens were collected for ND,H_5 and H_9 HI antibody test. It was showed by the results that for H_9 ten-day-old chicks are suitable for vaccination,but for H_5 antibody titer was not remarkable difference between five-day-old chicks and ten-day-old chicks, that the vaccine No. 6(from Guangdong No. 3 strain ) induced effective immune protectivity since 20 days post vaccination which remained till over 50-80 days old and the hightest antibody level against H_9 which reached a average titer of 6.72lb from 31 days to 80 days old, that the immune efficacy of the H_9 vaccine for use now in practice was not very good,but the immune efficacy of the H_5 vaccine for use now in practice was very good, that the effect of the vaccination dose (0.30 mL per chick or (0.25) mL per chick) of the H_5 vaccine on the immune efficacy was not obvious, but the effect of the vaccination dose 0.30 mL per chick was better than that of 0.25 mL per chick for H_9, and that either the age for vaccination or the dose vaccinated had little effect on the immune efficacy of the ND vaccine.