Curcumin modulates targeted gut bacterial populations and NF-κB/NRF2 immune-redox responses in Eimeria-challenged broilers fed soybean or canola oil

Avian coccidiosis compromises growth performance and gut health in broiler chickens. We investigated whether the dietary fat source (soybean oil vs. canola oil) and curcumin supplementation (0.02%) could enhance resilience to a mixed Eimeria challenge. In a 42-day trial, 660 one-day-old male Ross 308 broiler chicks were allocated to five treatments, with six replicates of 22 birds each: an unchallenged control group fed a soybean oil-based diet and four challenged groups fed soybean oil, soybean oil plus curcumin, canola oil, or canola oil plus curcumin. Challenged birds received an oral gavage of mixed Eimeria oocysts on day 14. Relative to the non-supplemented challenged control groups, the clearest pairwise recovery was observed in the canola oil plus curcumin group, whereas responses in the soybean oil plus curcumin group were more endpoint-dependent. Among challenged birds in the factorial analysis, curcumin improved body weight gain and feed efficiency; reduced abdominal fat and relative liver and spleen weights; improved lipid and hepatobiliary indices; increased post-challenge immunoglobulin levels; reduced NF-κB and IL-6 expression; increased IL-10 expression; enhanced total antioxidant capacity, superoxide dismutase and catalase activities; lowered malondialdehyde (MDA) and corticosterone levels; and upregulated NRF2 and SOD1. Culture-based enumeration showed that curcumin increased ileal and cecal Lactobacillus spp. counts and reduced ileal E. coli, with a tendency to reduce cecal E. coli. Canola oil produced limited endpoint-specific effects, mainly on feed intake, cholesterol, low-density lipoprotein cholesterol, alanine aminotransferase, MDA, and IL-6. Overall, curcumin partially mitigated coccidiosis-associated disturbances, although responses varied by endpoint and lipid background.