Postbiotic strategies alleviate negative effects of subacute ruminal acidosis (SARA) on digestive and immune health in lactating dairy cows
High-energy diets feeding in dairy farms can impact the homeostasis of gastrointestinal tract via changing the ecology of gut microbiota and their metabolites thus affecting the functionality of gut epithelium and host immune response, as a consequence, induce metabolic disorders in the body such as subacute ruminal acidosis (SARA). These disorders cause the changes in the fatty acid profile of the milk, affecting the welfare of dairy cows by increasing the incidence of infectious diseases such as systemic inflammation. Therefore, it is critical to find efficient solutions that optimize animal production without compromising gut health. It has been reported that Saccharomyces cerevisiae fermentation products (SCFP) as one of the postbiotics benefits rumen fermentation and overall performance in lactating dairy cows. However, cows respond differently to SCFP among studies. We speculate that this might be due to the fact that the mode of action of SCFP is not completely understood and as such the recommended dose of SCFP for each animal is not optimized. In this study, we conducted two grain-based SARA challenges in early lactation of dairy cows. We found grain-based SARA challenges increases the lipopolysaccharides (LPS) concentrations in the rumen and hindgut, the concentrations of acute phase proteins and pro-inflammatory cytokines in peripheral blood. Grain-based SARA reduces the richness and diversity of rumen liquid and solid microbiota, alters its taxonomic compositions and predicted carbohydrates and nitrogen metabolic pathways. Besides, grain-based SARA reduces the number of significant associations among different taxa, the diversity of hub taxa in microbial co-occurrence networks in rumen liquid and solid microbiota. We also investigated the possible benefit of two different SCFP (XPC, NutriTek) and the doses effect of NutriTek on immunity status and response, composition and functionality of microbial communities in the rumen and on to grain-based SARA challenges in lactating dairy cows. Our results showed that NutriTek with higher dose (38 g/d) helps to reduce pro-inflammatory status, improve the diversity and richness of the rumen liquid microbiota, promote the growth of cellulolytic bacteria in both rumen liquid and solid microbial communities, hence, attenuating adverse digestive and inflammatory responses associated with grain-based SARA challenges.