Evaluating the effects of red osier dogwood extract and grape pomace on growth performance, plasma biochemistry, intestinal morphology and microbiota, and immune and antioxidant status of broiler chickens challenged with heat stress

288 one-day-old Ross 308 broiler chicks were randomly allotted into 4 dietary treatments; 1)Control (CON; corn-wheat-soybean based diet), 2)CON + 0.05% bacitracin methylene disalicylate (BMD), 3)CON + 0.3% ROD, and 4)CON + 2.5% GP and raised for 28 d. On d 21-27, birds were exposed to either a thermoneutral (TN; 24°C±1) or heat stress (HS; 32-34°C for 8 hr/day). On d 28, twelve male birds per treatment/temperature group were euthanized for measuring blood and intestinal health parameters. 0.05% BMD and 0.3% ROD inclusion improved (P ≤ 0.05) the ABWG and FCR, compared to CON. HS reduced (P ≤ 0.05) AFI, bursa and spleen weights, plasma ALT, lipase, and CK but increased (P ≤ 0.05) ALP, serum immunoglobulins compared to TN birds. HS further reduced (P ≤ 0.05) duodenal VH:CD, jejunal VH and VH:CD but this was reversed by ROD and GP. 0.05% BMD and 2.5% GP increased (P < 0.001) the relative abundance of Blautia and Sellimonas compared to the CON diet. ROD increased (P = 0.010) the relative abundance of Faecalibacterium compared to the BMD diet. The results suggest that 0.3% ROD extract may function as an alternative to antibiotics in improving broiler growth performance and intestinal health.