Effects of dietary supplementation with encapsulated capsaicinoids on growth performance and cecal microbiota in broiler chickens

Capsaicinoids (CAPs) are widely investigated as natural alternatives to antibiotic growth promoters; however, most studies have examined capsaicin (CAP) alone, and the combined effects of CAP and dihydrocapsaicin (DHC) in encapsulated form remain largely unexplored in broilers. This study evaluated dietary encapsulated capsaicinoids (E-CAPs; 0.47% CAP and 0.22% DHC w/w) on growth performance, meat quality, serum biochemistry, antioxidant status, organ indices, intestinal morphology, and gut microbiota in Arbor Acres broilers. A total of 384 broilers were randomly assigned to a basal diet (CON) or diets supplemented with 150 mg/kg (LDC) or 450 mg/kg (HDC) E-CAPs. Compared with CON, HDC increased average daily gain and reduced the feed-to-gain ratio during the grower and overall periods (P < 0.05), whereas LDC showed limited effects. HDC also decreased serum alanine aminotransferase and total bile acid levels relative to CON (P < 0.05), without differences in other biochemical or antioxidant parameters or in organ indices and intestinal morphology, indicating good metabolic safety. Both LDC and HDC reduced crude fat content and thiobarbituric acid reactive substances levels in breast meat during refrigerated storage, without affecting meat color, compared with the CON group (P < 0.05). Relative to CON, HDC reduced the relative abundance of Actinomycetota and increased the relative abundances of Clostridium_innocuum, Alistipes, and Turicimonas (q < 0.05), accompanied by predicted enrichment of pathways related to bacterial secretion systems and antimicrobial resistance. Overall, supplementation with 450 mg E-CAPs/kg diet (≈3.1 mg total CAPs/kg) enhanced growth performance, improved meat quality, and beneficially modulated gut microbiota while maintaining metabolic and intestinal health, supporting the combined encapsulated CAP - DHC formulation as a safe and effective feed additive for broilers.