Effects of thymol on ruminal microorganisms

Area of Science:

• Rumen microbiology
• Animal nutrition
• Natural product chemistry

Background:

• Thymol is a phenolic compound known for inhibiting oral bacteria.
• Limited information exists on thymol's effects on ruminal microorganisms.

Purpose of the Study:

• To investigate the impact of thymol on the growth and lactate production of specific ruminal bacteria (Streptococcus bovis JB1 and Selenomonas ruminantium HD4).
• To evaluate thymol's effect on in vitro glucose fermentation by mixed ruminal microorganisms.

Main Methods:

• Bacterial cultures of S. bovis JB1 and S. ruminantium HD4 were exposed to varying concentrations of thymol.
• In vitro fermentation of glucose by mixed ruminal microorganisms was conducted with and without thymol.
• Growth, lactate production, glucose uptake, and fermentation end-product profiles were analyzed.

Main Results:

• Thymol inhibited growth and lactate production in both S. bovis JB1 and S. ruminantium HD4 in a dose-dependent manner.
• Higher thymol concentrations (180 microg/ml for S. bovis, 90 microg/ml for S. ruminantium) completely inhibited bacterial growth.
• Thymol decreased glucose uptake by both bacterial species.
• In mixed cultures, thymol increased pH and the acetate to propionate ratio, while decreasing methane, acetate, propionate, and lactate concentrations.

Conclusions:

• Thymol is a potent inhibitor of glucose fermentation by key ruminal bacteria S. bovis and S. ruminantium.
• Thymol alters ruminal fermentation, reducing methane and lactate but also decreasing volatile fatty acids like acetate and propionate.