Comparative evaluation of a novel phytochemical mixture and monensin on host- and pathogen-targeted strategies in broiler chickens challenged with Eimeria maxima

To unravel the differences between host- and pathogen-mediated responses, this study compared the efficacy and mechanisms of a novel phytochemical mixture and monensin in enhancing growth performance, intestinal health, and modulating gut microbiota in broiler chickens infected with Eimeria maxima (E. maxima). A total of 280 one-day-old male broiler chickens were randomly assigned using a randomized complete block design based on initial body weight (BW) and distributed into four dietary treatments with five chickens per cage: non-challenged control (NC), challenged control (PC), monensin-supplemented (MO), and phytochemical mixture (CPG)-supplemented groups. All chickens, except those in NC, were orally challenged with 10,000 E. maxima oocysts on day 15, and body weights were recorded on days 1, 8, 15, 21, and 23. Fourteen chickens per treatment were euthanized at 6 and 8 days post-infection for jejunal mucosa collection to analyze gene expression of cytokines, tight junction proteins (TJPs), nutrient transporters, TLR4 signaling, and antioxidant enzymes. Jejunal lesion scores, fecal oocyst shedding, and microbial composition were also assessed. Compared with the PC group, supplementation with both MO and CPG significantly reduced jejunal lesion scores and fecal oocyst shedding; however, the magnitude of reduction was greater with MO, resulting in more pronounced improvements in BW and feed conversion ratio. In E. maxima-infected broiler chickens, both treatments alleviated jejunal inflammation by modulating pro-inflammatory cytokine expression and TLR4 signaling; however, CPG was more actively involved in host-mediated responses through restoration of nutrient transporter and TJPs expression, maintenance of intestinal barrier integrity, and enhancement of antioxidant defenses. In contrast, MO acted more effectively on pathogen-related outcomes, such as reductions in oocyst shedding and lesion severity, and also induced distinct alterations in the jejunal microbiota based on microbial community and PICRUSt-based predictive functional analyses. Collectively, this study demonstrates that CPG contributes to the control of E. maxima infection in broiler chickens by simultaneously supporting host intestinal function and gut microbial balance through a mode of action distinct from the pathogen-targeted strategy of monensin.