Phloretin supplementation ameliorates intestinal injury of broilers with necrotic enteritis by alleviating inflammation, enhancing antioxidant capacity, regulating intestinal microbiota, and producing plant secondary metabolites

The present study aimed to explore the effects of dietary phloretin (PT) on growth performance, immune response, and intestinal function in broilers with necrotic enteritis (NE). A total of 288 1-day-old Arbor Acres chicks were assigned to 3 groups, with 8 replicates per group and 12 chicks per replicate. Over 6 weeks, birds were fed a basal diet or the same diet supplemented with 200 mg/kg phloretin. Birds in the challenged groups were inoculated with coccildia during d 7 to 9 and Clostridium perfringens(CP) during d 14 to 18. Results showed that CP and coccidia challenge reduced the average daily gain and average daily feed intake, increased the feed conversion ratio of broilers, induced inflammation and oxidative stress, and inhibited mRNA expression levels for genes associated with intestinal barrier and nutrient transporters (P < 0.05). PT addition to the feed improved growth performance at early phase improved intestinal morphology, and elevated antioxidant capacity via increasing the activity of total antioxidant capacity and superoxide dismutase in the ileum in broilers with necrotic enteritis (P < 0.01). Dietary PT regulated the intesetinal immune function as observed by the increases in the content of secretory IgA in the ileum and decreased cytokines (Interleukin-1β, Interleukin-10) (P < 0.05). Moreover, NE infection significantly disrupted the balance of intestinal flora, and led to a lower level of short-chain fatty acids such as butyric acid concentration in the ileum, while PT improved the microbiota structure, and increased the intestinal acetic acid and butyric acid concentration (P < 0.001). Furthermore, metabolomics analysis indicated PT treatment improve plant secondary metabolites contents like phloretin 2'-o-glucuronide. Additionally, we observed a significant positive correlation among PT, Ligilactobacillus and butyric acid, and a positive correlation between Ligilactobacillus and plant secondary metabolites. Overall, PT supplementation could improve growth performance and ameliorate intestinal injury in broilers with necrotic enteritis by enhancing the antioxidant capacity and immune function, regulating intestinal flora structure and producing plant secondary metabolites.