Effects of various adjuvants on efficacy of a vaccine against Streptococcus bovis and Lactobacillus spp in cattle

Objective-To determine efficacy of Vaccines incorporating QuilA, alum, dext ran combined with mineral oil, or Freund adjuvant for immunization of feedl ot cattle against Streptococcus bovis and Lactobacillus spp. Animals-24 steers housed under feedlot conditions. Procedure-Steers were randomly assigned to 4 experimental groups and a cont rol group. Animals in experimental groups were inoculated on days 0 and 26 with Vaccines containing Freund adjuvant (FCA), QuilA, dextran combined wit h mineral oil (Dex), or alum as adjuvant. Serum anti-S bovis and anti-Lacto bacillus IgG concentrations were measured, along with fecal pH, ruminal flu id pH, and number of S bovis and Lactobacillus spp in ruminal fluid. Results-Throughout the study, serum anti-S bovis and anti-Lactobacillus IgG concentrations for animals in the Dex, QuilA, and alum groups were similar to or significantly higher than concentrations for animals in the FCA grou p. Serum anti-S bovis and anti-Lactobacillus IgG concentrations were signif icantly increased on days 26 through 75 in all 4 experimental groups, and t here was a linear relationship between anti-S bovis and anti-Lactobacillus IgG concentrations. For animals in the QuilA and Dex groups, mean pH of fec es throughout the period of experiment were significantly higher and number s of S bovis and Lactobacillus spp in ruminal fluid on day 47 were signific antly lower than values for control cattle. Conclusions and Clinical Relevance-Results suggest that immunization of fee dlot steers against S bovis and Lactobacillus spp with vaccines incorporati ng Freund adjuvant, QuilA, dextran, or alum as an adjuvant effectively indu ced high, long-lasting serum anti-S bovis and anti-Lactobacillus IgG concen trations. Of the adjuvants tested, dextran may be the most effective.