Effects of Scrophularia striata hydroalcoholic extract in comparison to salinomycin on growth performance, intestinal health and immunity in broiler chickens following a mixed-species Eimeria challenge

Abstract

Poultry coccidiosis is an important disease affecting performance which is characterized by intestinal epithelium damageand increased mortality and is caused by the protozoa parasites of the genus Eimeria. This study evaluated the growth-promoting (experiment 1), protective, and immunostimulatory effects (experiment 2) of salinomycin and Scrophularia striata hydroalcoholic extract (SSE) against coccidiosis in broilers. Two experiments were conducted with 300 1-day-old broiler chickens, which were randomly assigned to 5 treatments with 6 replicate pens of 10 birds (experiment 1) or 10 replicate cages of 6 birds (experiment 2). In both experiments, treatments were: negative control (NC: untreated, and uninfected); positive control (PC: untreated, infected); or PC supplemented with salinomycin (Sal); 200 mg/kg of SSE (SSE200); or 400 mg/kg of SSE (SSE400). All these groups (except NC) were challenged via oral gavage with of sporulated oocysts of Eimeria species (Eimeria acervulina, Eimeria maxima, and Eimeria tenella) on d 10 (experiment 1) or d 14 (experiment 2). In the first trial, all treatments improved growth and feed conversion compared with the PC group, where the best values were noticed in the NC, SAL, and SSE400 groups throughout the entire experimental period (d 1–42). Further, a lower mortality rate (P < 0.05) was observed in the NC, Sal, and SSE400 groups as compared to that in the PC group. In the second trial, intestinal lesion scores and total oocyst numbers were reduced in the Sal and SSE400 groups compared to the PC group, although all coccidiosis-challenged groups had higher intestinal lesion scores (P < 0.05) compared to NC group. Immune responses revealed that among challenged birds, those fed diets Sal and SSE400 had significantly higher Eimeria-specific cecum IgG and IgM levels, but lower serum IFN-γ concentration than the PC group. Among the experimental treatments, broiler chickens fed diet SSE400 had greater (P < 0.05) Eimeria-specific serum IgG and TGF-β levels, but lower (P < 0.05) serum IL-6 concentration than those fed the PC diet at d 24. Considering the results, dietary SSE, especially at high levels of inclusion in broiler diet (400 mg/kg), could result in a comparable growth performance and a better immune response, compared to a salinomycin supplement under coccidiosis challenge.