How High dCO2 Fuels LPS Production in Ruminal Bacteria
Ruminal acidosis is often linked to high levels of Lipopolysaccharides (LPS) – bacterial toxins that trigger inflammation. While the presence of LPS in the rumen is established, the factors influencing its production haven't been entirely clear.
My recent research sheds light on a potential culprit: high dissolved CO2 (dCO2) within the rumen.
The Link Between dCO2 and LPS Production
Studies by Dain et al. (1956), Wright (1960), and Cheng et al. (1976) observed a fascinating phenomenon – increased LPS production in bacteria like S. Bovis under high CO2 conditions. This suggests a direct link between dCO2 levels and bacterial LPS synthesis. Bailey's work in 1959 further strengthens this connection by suggesting a specific enzyme involved in LPS formation might require high dCO2 levels for its activity.
CO2 Holdup: The Bridge Between Diet and High dCO2
Normally, CO2 produced by rumen microbes exits through eructation (burping). However, some diets might limit CO2 effervescence leading to CO2 holdup or critical dCO2 levels within the rumen fluid for extended periods.
The Chain Reaction: From High dCO2 to LPS Translocation
High dCO2 due to CO2 holdup might trigger a cascade of events that contribute to LPS translocation (movement of LPS into the bloodstream):
Increased LPS Production: As suggested by the studies mentioned earlier, high dCO2 might activate the LPS-forming enzyme, leading to increased LPS production by ruminal bacteria.
Hyperemia and Epithelial Disruption: the exposure of local tissue to high CO2 increases blood flow (Diji & Greenfield, 1960; Kontos et al., 1967; Richardson et al., 1961) and ruminal dCO2 increases blood flow into the epithelium or “hyperaemia” (Thorlacius, 1972). Extended periods under hyperaemia might induce hypoxia and inflammatory response of the GIT (Glover & Colgan, 2017), as seen during SARA and associated to LPS exposure in in vitro (Kent-Dennis & Penner, 2021).
LPS Translocation: in vivo, the presence of ruminal LPS not always lead to SARA signs (Khafipour et al., 2009a, 2009b). In fact, high dCO2 induced hyperaemia might disrupt epithelial barrier (Celebi Sozener et al., 2022; Lang et al., 2000) and LPS might, per se, not (McDaniel et al., 2023).
Beyond LPS Production: Other Potential Effects of High dCO2
While research on the specific effects of high dCO2 on rumen bacteria is ongoing, some studies suggest it might also influence:
Maintaining Cell pH: High CO2 can lead to internal acidification in bacteria. LPS might help regulate the influx of ions and maintain internal pH homeostasis (Bailey, 1959).
Nutrient Acquisition: Some bacteria can utilize CO2 as a carbon source. LPS production might be linked to the metabolic pathways involved in CO2 fixation (Bailey, 1959).
Cell Wall Reinforcement: LPS strengthens the cell wall. In a high CO2 environment, the bacteria might need a more robust cell wall to withstand the pressure changes or other environmental stresses (Bailey, 1959).
Preventing CO2 Holdup: A Key Strategy
By preventing CO2 holdup, we can potentially interrupt this chain reaction at its source. Dietary strategies that promote slower, more controlled fermentation, such as providing adequate fiber, can help manage CO2 production. Additionally, innovative technologies for continuous dCO2 monitoring could be valuable tools for early detection and prevention of CO2 holdup.
Conclusion
By focusing on preventing CO2 holdup, we can potentially develop more effective strategies to minimize LPS translocation and the associated problems of acidosis in ruminant animals. This not only improves animal health and well-being but also contributes to a more sustainable and productive livestock industry.
