Effects of probiotic bacteria at different concentrations on production of immunomodulatory antibodies against rabies virus in vaccinated cattle

This study evaluated the effects of supplementation with a combination of probiotic microorganisms, added at different concentrations to the mineral mixture, on the production of serum antibodies against rabies virus in cattle vaccinated with a single dose of rabies vaccine. Forty-two male Nellore cattle, aged 12 months, were randomly divided into three groups (n = 14): the control group (CG) received 70 grams of mineral mixture/animal/day; and the 2 gram probiotic group (G2P) and 8 gram probiotic group (G8P) received 70 grams of mineral mix/animal/day with 2 and 8 grams added, respectively, of a combination of probiotic microorganisms (Lactobacillus acidophilus, Streptococcus faecium, Bifidobacterium thermophilum and Bifidobacterium longum). Individual antibody titers were determined using a neutralization in cell-based rapid fluorescent focus inhibition test (RFFIT) technique. One-way analysis of variance (one-way ANOVA) was used with contrasts using the Tukey method to determine whether the experimental groups differed within each time point, and the paired t-test was used to determine whether differences occurred between time points within each group. The level of significance was set at 5%. There were statistically significant differences between the mean serum concentrations of the CG and G8P groups at 30 and 60 days after the first vaccination, and at 60 days, 100% of the animals maintained minimum titers of protective antibodies only in the G8P group. There was also improvement in the production of antibodies in the G2P group compared with the CG after 30 and 60 days, but this difference was not statistically significant. In conclusion, increasing doses of probiotic added to the mineral mix beneficially affected the rabies humoral immune response, as determined by serum antibodies, and enabled the maintenance of minimum protective titers for a longer period in previously vaccinated cattle.