Effect of an intramammary lipopolysaccharide challenge on the hindgut microbial composition and fermentation of dairy cattle experiencing intermittent subacute ruminal acidosis

Feeding grain-rich diets often results in subacute ruminal acidosis (SARA), a condition associated with dysbiosis and systemic inflammation. Yet, the effect of SARA on hindgut microbiota, whether this is aggravated by exogenous immune stimuli, less understood. Therefore, aims study were to determine effects an intermittent high-grain model microbial community, evaluate fecal microbiome fermentation further affected intramammary lipopolysaccharide (LPS) challenge. A total 18 early-lactating Simmental cows divided into 3 groups (n = 6); 2 fed SARA-inducing feeding regimen (60% concentrate), 1 was control (CON) diet (40% concentrate). On d 30, group (SARA-LPS) CON (CON-LPS) intramammarily challenged single dose 50 µg LPS from Escherichia coli O26:B6, whereas remaining 6 (SARA-PLA) received placebo. Using longitudinal randomized controlled design, grouping according parity days milk), statistical analysis performed baseline measurements used as covariate mixed procedure. The challenge resulted decreased pH increased butyrate proportion short-chain fatty acids feces. SARA-challenged had diversity shown Shannon Chao1 indices decrease relative abundance Euryarchaeota cellulolytic genera, numerical increases several Firmicutes starch secondary fermentation. did not affect acids, but richness index interaction challenge, Verrucomicrobia (1.13%), Actinobacteria (0.19%), Spirochaetes (0.002%), suggesting ecology during conditions. In conclusion, promoted important changes at including reduced evenness compared CON, external led community without affecting properties.