Eco-friendly zinc nanoparticles biosynthesized by Lactobacillus casei as alternative anticoccidial agent ameliorate Eimeria tenella infection in broiler chickens: Impact on oxidative stress, intestinal health, growth performance, and gut microbiota

• Coccidiosis is a parasitic infection affecting poultry farms worldwide. • Eco-friendly zinc nanoparticles were produced using a green method involving Lactobacillus casei (Lc-ZnNPs). • Lc-ZnNPs showed promising results in reducing the severity of Eimeria tenella infection. • Lc-ZnNPs helped maintain a healthy gut environment in the chickens, which is crucial for nutrient absorption and overall. • Chickens treated with Lc-ZnNPs exhibited better growth performance and balanced and beneficial gut microbial community. Coccidiosis, a parasitic infection caused by Eimeria species poses significant challenges to poultry farms worldwide. Despite extensive control efforts, the disease continues to impact poultry health and productivity. Recently, green-synthesized nanoparticles have emerged as a promising area in nanotechnology for combating infections. This study evaluates the potential of Lactobacillus casei EE12-mediated zinc nanoparticles (Lc-ZnNPs) as an alternative anticoccidial agent in Eimeria tenella -infected broiler chickens and assesses their effects on growth performance, oxidative status, immunity, gut microbiota, and inflammatory responses. Zinc nanoparticles fabricated by the Lactobacillus casei EE12 supernatant were spherical, 41 nm, -24.4 mV charged, and surrounded with active groups. A total of 360 broiler chickens were equally divided into 6 groups: C) the control received basal diet; T1-T3) received basal diet supported with Lc-ZnNPs at different concentrations (25, 50, and 75 mg/kg diet); T4) E. tenella -infected group were infected orally through a stomach tube, with 5 × 10 4 sporulated oocysts of Eimeria tenella , and T5) E. tenella -infected broilers supplemented with Lc-ZnNPs (75 mg/kg diet). Adding Lc-ZnNPs to the broiler diet significantly improved growth performance markers, including body weight gain (BWG), feed intake (FI) & feed conversion ratio (FCR) compared to the control and infected groups. The Eimeria -infected broilers showed higher levels of AST, ALT, uric acid, total cholesterol, MDA, & LDL. Meanwhile, the addition of Lc-ZnNPs (75 mg/kg) mitigated the oxidative stress by lowering MDA and enhancing the activity of SOD, CAT, & GPx besides the immunity markers. Also, downregulating the intestinal, hepatic, & kidney proinflammatory markers (Mucin-1, OCCU & interleukin-6, & IL-1β) and proapoptotic (Bcl-2-associated protein x & Casp-3) markers. Lc-ZnNPs significantly ( P < 0.05) reduced oocyst per gram (OPG) by 67 % and lesion score, recovering the typical structure of intestines. The E. tenella -infected broilers showed higher total bacterial count (TBC), total yeasts and molds count (TYMC), and Salmonella count; meanwhile, the Lc-ZnNPs-treated birds in T5 significantly ( P < 0.05) reduced these counts and enhanced the lactic acid bacteria (LAB) count compared to the T4 and control group. In conclusion, the findings indicated that Lc-ZnNPs could be a safe and potent anticoccidial agent against coccidiosis in broiler chickens.