Vanillin Improves Antioxidant Capacity, Immunity, and Gut Microbiota in Broilers

Wle vanillin is widely used as a flavoring agent in food products, its potential as a non-antibiotic feed additive for broilers remains unexplored. This study primarily investigated the effects of dietary supplementation of vanillin on antioxidant activity, anti-inflammatory response, immune function, and gut microbiota composition in broilers. One-day-old male broilers were randomly assigned to five groups: a basal diet group, a positive control group (basal diet + 100 mg/kg chlortetracycline (CTC)), and three vanillin-supplemented groups (0.1%, 0.2%, or 0.4%) for 42 days. Results showed that vanillin improved antioxidant capacity, with elevated serum superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity and reduced malondialdehyde (MDA) levels. Broilers receiving vanillin supplementation showed lower levels of pro-inflammatory cytokines (interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α)) and higher interleukin-10 (IL-10) expression compared with controls. Additionally, serum immunoglobulin A (IgA) and immunoglobulin M (IgM) levels were also greater in the vanillin group. It also enhanced intestinal health by increasing the duodenal villus height-to-crypt depth ratio, improving intestinal morphology, raising the Firmicutes-to-Bacteroidetes ratio, and promoting Lactobacillus proliferation compared with CTC. Notably, growth performance data were exploratory in nature; vanillin was associated with numerical improvements in average daily gain (ADG) and feed conversion (F/G) ratio. These preliminary findings suggest that vanillin requires further investigation as a potential feed additive.