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

A total of 288 1-day-old Ross 308 broiler chicks were randomly allotted into four dietary treatments: (1) Control (CON; corn–wheat–soybean-based diet), (2) CON + 0.05% bacitracin methylene disalicylate (BMD), (3) CON + 0.3% red osier dogwood extract (ROD), and (4) CON + 2.5% grape pomace (GP) and raised for 28 days. On days 21–27, birds were exposed to either a thermoneutral (TN; 24 ± 1 °C) or heat stress (HS; 32–34 °C for 8 h/day) environment. On day 28, 12 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 average body weight gain and feed conversion ratio, compared to CON. HS reduced ( P ≤ 0.05) average feed intake, bursa and spleen weights, plasma alanine transferase, lipase, and creatinine kinase but increased ( P ≤ 0.05) alanine phosphatase and serum immunoglobulins compared to TN birds. HS further reduced ( P ≤ 0.05) duodenal villus height (VH):crypt depth (CD), jejunal VH, and VH:CD but this was reversed by ROD and GP, and 0.05% BMD and 2.5% GP increased ( P