Characterization of microbial intolerances and ruminal dysbiosis towards different dietary carbohydrate sources using an in vitro model

AIM: This study aimed to characterize the critical points for determining the development of dysbiosis associated with feed intolerances and ruminal acidosis. METHODS AND RESULTS: A metabologenomics approach was used to characterize dynamic microbial and metabolomics shifts using the rumen simulation technique (RUSITEC) by feeding native cornstarch (ST), chemically modified cornstarch (CMS), or sucrose (SU). SU and CMS elicited the most drastic changes as rapidly as 4 h after feeding. This was accompanied by a swift accumulation of d‐lactate, and the decline of benzoic and malonic acid. A consistent increase in Bifidobacterium and Lactobacillus as well as a decrease in fibrolytic bacteria was observed for both CMS and ST after 24 h, indicating intolerances within the fibre degrading populations. However, an increase in Lactobacillus was already evident in SU after 8 h. An inverse relationship between Fibrobacter and Bifidobacterium was observed in ST. In fact, Fibrobacter was positively correlated with several short‐chain fatty acids, while Lactobacillus was positively correlated with lactic acid, hexoses, hexose‐phosphates, pentose phosphate pathway (PENTOSE‐P‐PWY), and heterolactic fermentation (P122‐PWY). CONCLUSIONS: The feeding of sucrose and modified starches, followed by native cornstarch, had a strong disruptive effect in the ruminal microbial community. Feed intolerances were shown to develop at different rates based on the availability of glucose for ruminal microorganisms. SIGNIFICANCE AND IMPACT OF THE STUDY: These results can be used to establish patterns of early dysbiosis (biomarkers) and develop strategies for preventing undesirable shifts in the ruminal microbial ecosystem.