Influence of phytochemicals on growth performance, gut morphology and ceca microbiome in broilers fed aflatoxin-contaminated diet and raised under high stocking density and heat stress

This study evaluated the effects of phytochemicals on growth performance, immune response, gut morphology, and cecal microbiome of broilers fed an aflatoxin-contaminated diet under high stocking density and heat stress. A total of 2,800 one-day-old male Ross 308 broiler chicks were raised at 18 birds/m² during the summer. The birds were assigned to seven dietary treatments: (1) corn-soybean meal basal diet (CON), (2) CON + 50 ppb aflatoxin (AFT), (3) AFT + 50 ppm bacitracin (BCT), (4) AFT + 300 ppm flavanone (FVN), (5) AFT + 80 ppm isoquinoline alkaloids (IQA), (6) AFT + FVN (1-10 days) and IQA (11-37 days) (FVN-IQA), and (7) AFT + IQA (1-10 days) and FVN (11-37 days) (IQA-FVN) for 37 days. The heat stress index exceeded 160 for most of the experimental period. Feed efficiency was significantly lower in the AFT group than in the CON, FVN, IQA, and combination groups, while the BCT group showed no significant difference from others. The heterophil-to-lymphocyte ratio was higher in the AFT group than in the CON, IQA, FVN-IQA, and IQA-FVN groups. The AFT group exhibited higher interleukin-6 levels than other groups. Serum malondialdehyde was lower in the CON, FVN, and IQA-FVN groups than in the AFT group. Duodenal and jejunal villi height and villi height-to-crypt depth ratio were reduced in the AFT group. The AFT group showed reduced α-diversity, evaluated by Chao1 and Shannon indices. Treatment groups significantly affected β-diversity and microbiota composition at the phylum, family, and species levels. Compared to the CON group, AFT altered 125 metabolic pathways, while BCT, FVN, IQA, FVN-IQA, and IQA-FVN altered 347, 91, 38, 153, and 396 metabolic pathways, respectively, relative to the AFT group. Exposure to 50 ppb aflatoxin under high stocking density and heat stress impaired feed efficiency, immune status, and gut health in broilers. Supplementation with FVN, IQA, or their combinations mitigated these effects, with the combinations showing the greatest efficacy.