One of the most prevalent causes of gastrointestinal disease in humans is Campylobacter jejuni, and chickens are recognized to be the most common hosts. Scrophularia striata hydroalcoholic extract (SSE) and mannan-oligosaccharide were used in a six-week pilot-scale study to assess their effectiveness against C. jejuni. A total of 560 one-day-old male broiler chickens (Ross 308) were randomly assigned to 5 groups with 8 replicates of 14 birds each. The experimental groups were as follows: negative control (NC; untreated, and uninfected); positive control (PC; untreated, infected with C. jejuni); PC + mannan-oligosaccharide (MOS); PC + 200 mg/kg of SSE (SSE200); or PC + 400 mg/kg of SSE (SSE400). All these groups (except NC) were challenged with C. jejuni on day 15. On days 15, 24, and 42, ileal and cecal digesta samples were collected for quantification of Lactobacillus spp., C. jejuni, and Coliforms. On days 24 and 42, blood samples were also collected in order to examine serum concentrations of immunoglobulins (IgA, IgG, and IgM), interleukin-6 (IL-6), and gamma interferon (IFN-γ). The results showed that decreases in final body weight, average daily gain, feed intake, and increases in overall feed conversion ratio, mortality rate, cecal coliform counts (days 24 and 42), and blood IL-6 and IFN-γ concentrations (day 24) induced by Campylobacter infection were restored in birds fed diets MOS and SSE400 to a level that was not significantly different from the NC treatment. On days 24 and 42, the population of Coliforms in the ileum was also lower (P < 0.05) in broiler chickens fed the SSE400 diet compared to chickens fed the PC diet. Among challenged birds, those fed diets MOS and SSE400 exhibited lower (P < 0.05) ileal and cecal counts of C. jejuni (days 24 and 42), but higher (P < 0.05) serum IgG (days 24 and 42) and IgA (day 24) concentrations than the PC group. In conclusion, the SSE-supplemented diet at an inclusion level of 400 mg/kg could ameliorate the detri
