Study on the First Immunization Time of Calf Brucellosis Vaccine
To investigate the first immunization time of live calf brucellosis vaccine(A19 strain)and to understand the fluctuation rule of humoral immune response antibody,so as to develop the immunization program of live calf brucellosis vaccine in this area,a total of 1306 calves from 1 to 12 days of age were selected from 10 local large-scale dairy farms(more than 700 adult dairy cows),and were continuously tested until 12 months of age.The health status of cattle before and after immunization was observed,the concentration of main immunized cattle in practice,the fluctuation of calf maternal proto-antibody before immunization and the fluctuation of antibody after immunization at different months were monitored.Combined with many years of clinical operation practice(mainly selected immune time point,environment and climate for easy operation),sexual organs before maturity,calving time,number of calves,personnel arrangement and other situations were summarized and analyzed.The calves were safe after immunization.In practice,the immunized calves mainly concentrated in 3～5 months of age.Before immunization,the maternal proto-antibody of calves was nearly zero at 5 months of age,and the humoral immune response was stronger at 3 to 5 months of age.It is recommended that the first free time of calves should be 3 to 5 months old.
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