DOI: 10.33988/auvfd.1892357 ISSN: 1300-0861

Effects of capsaicin on rumen fermentation under normal and acidosis pH conditions: A comparative Rusitec study with monensin

Melis Unler, Hakan Öztürk
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Capsaicin (CAP), the pungent component of chili peppers, possesses antimicrobial activity against a broad range of bacteria. This study evaluated the in vitro effects of CAP on ruminal fermentation under normal and acidic (SARA) pH conditions using the Rusitec system, in comparison with monensin (MON). By isolating pure capsaicin and applying a controlled dual-pH design, this study addresses uncertainty regarding CAP’s specific regulatory role in the rumen, thereby distinguishing its effects from those of complex phytochemical blends. The 18-day trial included adaptation, normal fermentation, and acidosis phases. CAP was tested at 1, 5, and 25 mg/L alongside MON (5 mg/L) under a high-concentrate diet (20:80). CAP significantly reduced ruminal pH at all doses, while SARA induction caused a clear phase-dependent pH decline in all fermenters. Total volatile fatty acids (VFA) production was unaffected by treatments but decreased during acidosis. MON increased propionate under both pH conditions, whereas CAP showed no effect. Only the CAP5 and CAP25 groups had higher methane production than the MON group. Protozoal counts were lowest in the MON group. NH₃-N and dry matter digestibility declined solely due to acidosis. Overall, at the tested doses, CAP exerted minimal influence on ruminal fermentation compared with MON.

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