ISSUE FOCUS 46 FEED & ADDITIVE MAGAZINE March 2022 HOW DO ENDOTOXINS AND RUMEN HEALTH INFLUENCE COW PERFORMANCE? In which cases can LPS (endotoxins) cause inflammation and contribute to different metabolic conditions and diseases, affecting animal performance? Sub-acute rumen acidosis (SARA) is linked to high levels of ruminal LPS. The LPS cause inflammation and contribute to different metabolic conditions and diseases. Various strategies and solutions can be applied to modulate the rumen microbiota and prevent this risk. In sub-acute rumen acidosis (SARA), the quantity of free lipopolysaccharides (LPS) coming from Gram- bacteria increases considerably. These LPS cross the ruminal wall and intestine, passing into the bloodstream. The negative consequences on the health of the animal are then reflected in decreased productive and reproductive performance. The LPS are released during the lysis of Gram- bacteria that die due to the low pH. These bacteria are mainly responsible for propionic acid production for the obtained energy yield. It is essential to preserve ruminal balance between Gram+ and Gram- such that there is no excess of LPS. WHAT IS RUMEN ACIDOSIS? Rumen acidosis is that "pathology" whereby the volume of SCFA (Short Chain Fatty Acids) produced by the rumen bacteria is greater than the ability of the rumen itself to absorb and neutralize them. Rumen acidosis is mainly caused by the amylolytic and saccharolytic bacteria (Streptococcus bovis; Selenomonas ruminantium, Bacteroides amylophilus, Bacteroides ruminicola, and others) responsible for the production of lactic acid. Unlike the other most representative volatile fatty acids (acetic, butyric, and propionic), lactic acid has a lower pKa: 7 (3.9 versus 4.7). This means that for the same amount of molecules produced, lactic acid releases a number of ions H+ in the fluid ten times greater than other VFAs, with evident effects on the pH. Ruminal acidosis can be characterized as acute or subacute. During acute ruminal acidosis, the pH in the rumen drops below 4.8 and remains low for an extended period of time. Acute acidosis leads to complete anorexia, abdominal pain, diarrhea, lethargy, and eventually death. However, the prevalence of acute acidosis in dairy is very low. CONSEQUENCES OF RUMEN ACIDOSIS In such situations, a series of negative consequences can be triggered in the lactating cow. Investigations (for instance, using fistulated cows) can reveal, among others, the following alteration in the rumen: • Shift in total microbiome rumen profile (density; diversity; community structure) • Shift in protozoa population (increase in ciliates protozoa after 3 weeks of SARA; increase in the GNB population) Claudio Campanelli Technical Manager – Ruminants EW Nutrition
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