In vitro evaluation of selected compounds affecting ruminal fermentation and methane production

Area of Science:

• Ruminant nutrition and metabolism
• Environmental microbiology
• Agricultural chemistry

Background:

• Rumen fermentation produces volatile fatty acids (VFA) essential for host energy but also generates methane (CH4), representing dietary energy loss.
• Feed additives like nitro compounds and phytochemicals can mitigate CH4 emissions, yet their impact on VFA synthesis requires careful in vitro evaluation.

Purpose of the Study:

• To screen compounds for CH4 reduction potential in rumen fermentation.
• To determine effective, non-inhibitory doses of selected additives.
• To assess the combined effects of carvacrol (CAR) and 2-nitroethanol (2NEOH) on rumen fermentation parameters.

Main Methods:

• Three sequential in vitro assays were performed.
• Eleven compounds were screened for CH4 reduction; CAR and 2NEOH were selected.
• Dose-response (0-10 mM) and combination studies (LOW: 1.25 mM each; HIGH: 2.5 mM each) evaluated VFA, gas production (CH4, CO2, H2), pH, and in vitro dry matter digestibility (IVDMD).

Main Results:

• Carvacrol (CAR) and 2-nitroethanol (2NEOH) significantly reduced CH4 by at least 20%.
• High doses of CAR and the CAR+2NEOH combination drastically reduced CH4 but also VFA production and increased H2.
• Low-dose CAR+2NEOH reduced CH4 (18%) and the acetate-to-propionate ratio, with performance similar to 2NEOH alone.

Conclusions:

• CAR and 2NEOH exhibit distinct effects on rumen fermentation and methanogenesis.
• High-dose combinations negatively impact overall fermentation; low-dose combinations show promise for CH4 mitigation without compromising VFA production.
• Further research into rumen microbial modulation by these compounds is needed for in vivo application.