Dietary honokiol supplementation improves antioxidant capacity, enhances intestinal health, and modulates cecal microbial composition and function of broiler chickens

Honokiol is a multifunctional polyphenol present in Magnolia officinalis. The effects of honokiol as a supplement in broiler chicken diets, and the underlying mechanisms, remain unclear. Therefore, the aim of the present study was to investigate the effects of honokiol on the growth performance, antioxidant capacity, and intestinal histomorphology of broiler chickens and to explore the underlying mechanisms. In total, 240 1-day-old broilers were randomly allocated to five dietary treatments, with six replicate pens and eight birds per pen. Birds were fed a basal diet supplemented with 0 (blank control, BC), 100, 200, or 400 mg/kg honokiol (H100, H200, and H400), or 200 mg/kg bacitracin zinc (PC) for 42 days. The results showed that H200 and H400 increased body weight gain (BWG) and decreased feed conversion ratio (FCR) during the starter period (P < 0.05). H100 and H200 increased total superoxide dismutase (T-SOD) activity in the serum and decreased malondialdehyde (MDA) amount in the jejunum on day 42 (P < 0.05). Moreover, H100 increased villus height-to-crypt depth ratio in both the jejunum and ileum on day 21 (P < 0.05). PCR analysis showed that honokiol upregulated intestinal expression of glutathione peroxidase (GSH-Px) and downregulated intestinal expression of inducible nitric oxide synthase (iNOS) on day 42 (P < 0.05). The Shannon index, which represents the microbial alpha diversity, was reduced for the PC, H200, and H400 groups. Notably, honokiol treatment altered the cecal microbial community structure and promoted the enrichment of several bacteria, including Firmicutes and Lactobacillus. Higher production of short-chain fatty acids was observed in the cecal digesta of H100 birds, accompanied by an enriched glycolysis/gluconeogenesis pathway, according to the functional prediction of the cecal microbiota. This study provides evidence that honokiol improves growth performance, antioxidant capacity, and intestinal health of broiler chickens, possibly by manipulating the composition and function of the microbial community.