Curcumin-mediated resilience to mixed Eimeria challenge in broilers fed soybean or canola oil: growth performance, hematology, coccidial lesions, oocyst shedding, digestibility, and intestinal barrier biology.

A 42-day study evaluated whether dietary fat source (soybean oil vs. canola oil) and curcumin supplementation enhance broiler resilience to coccidiosis. In total, 660 Ross 308 male broilers were assigned to a completely randomized design with five treatments (6 replicates per treatment; 22 birds per replicate): (1) unchallenged control with soybean oil; (2) soybean oil + coccidiosis challenge; (3) soybean oil + 0.02% curcumin + challenge; (4) canola oil + coccidiosis challenge; and (5) canola oil + 0.02% curcumin + challenge. On day 14, challenged birds received a 1 mL oral gavage of sporulated oocysts (50,000 Eimeria acervulina, 10,000 E. maxima, and 5,000 E. tenella per bird), whereas unchallenged birds received sterile saline. The challenge impaired growth and feed efficiency and increased mortality, accompanied by higher intestinal lesion scores and oocyst shedding, reduced nutrient utilization, disrupted villus-crypt architecture and goblet cell counts, and downregulated jejunal barrier-associated transcripts (P < 0.05). Curcumin (0.02%) mitigated these effects by improving body weight at days 24 and 42, increasing average daily gain during days 11-24 and across days 1-42, improving feed conversion ratio during days 11-24 and overall, reducing mortality, and increasing the European performance index (P < 0.05). Curcumin also reduced duodenal and cecal lesion severity, decreased fecal oocyst shedding across post-challenge intervals, improved crude protein and ash digestibility, and restored intestinal morphology (greater villus height and surface area, a higher villus height-to-crypt depth ratio, and increased goblet cell counts) (P < 0.05). Hematological measures further supported improved resilience, with lower heterophil counts and heterophil-to-lymphocyte ratio and higher hematocrit (P < 0.05). At the molecular level, curcumin upregulated jejunal CLDN1 and MUC2, whereas OCLN and ZO1 were unchanged (P < 0.05). In conclusion, these findings show that 0.02% curcumin strengthens intestinal integrity and reduces parasite burden, translating into measurable improvements in flock-level performance under coccidiosis challenge and supporting its practical use as a nutrition-based strategy to enhance disease resilience.