FIGURE 6.

Protective rates of Bordetella avium-challenged chickens. Chickens in four groups were inoculated with ompA subunit vaccine, ompA–Fc subunit vaccine, TPPPS adjuvant ompA–Fc vaccine, and PBS at 1, 7, and 14 dpv. One week after the third vaccination, 20 chickens from each group were challenged intranasally with 10 LD₅₀ of B. avium LL strain. Morbidity (A) and protective rate (B) were monitored for seven successive days after challenge. Morbidity (%) = No. of chickens with clinical symptoms/Total No. × 100. (B) Protective rate (%) = No. of chickens without clinical symptoms/Total No. × 100. Values shown represent the means ± SD for three independent experiments. Different lowercase letters above the columns indicate significant differences between the different groups (P ≤ 0.05).