Abstract: This test using totle 9 head of cattles,which were 3 to 6 month old healthy and susceptible (IBRVand BVDV antigen negtive,antibody titer is less than or equal to 2),were divided into 3 groups,each group of 3 cows. The first group was injected with IBRV-LNM attenuated vaccine strain,one weeks later each animal was inoculated with BVDV-SM attenuated vaccine strain. The second group was only inoculated with BVDV-SM attenuated vaccine strain at the same time with the first group. The third group was the control group and inoculated with MDBK cell culture fluid. the determination of BVDV antibody titer post-vaccination every week until 28 days,and then challenged with BVDV-JL virulent strain. The results showed that the serum of bovine viral diarrhea virus antibody levels had no significant differences between the first and the second group, and observation after the challenge showed that the vaccine effectively protected calves from the challenge.This suggested that IBRV attenuated strain was not restrained BVDV attenuated vaccine virus in vivo.

Key words: infectious bovine rhinotracheitis virus; bovine viral diarrhea virus; immune inhibition