Multi-omics in vitro study of the salivary modulation of the rumen microbiota and its activity. Salivary modulation of the rumen microbiota

The role of the salivary components other than ions has not been thoroughly investigated in ruminants. Several salivary bioactive components (e.g. immunoglobulins) have been demonstrated to modulate the rumen microbial composition. This study used rumen fluids from 4 donor goats, which were incubated in a semi-continuous culture with autoclaved saliva (AUT), saliva from the same rumen fluid donor (OWN), GOAT saliva or SHEEP saliva. Fermentation was monitored throughout the 7 days of incubation and the prokaryotic communities and metabolome were analysed at days 6-7 of incubation. Characterization of the salivas used prior incubation showed a high degree of individual variability in terms of the salivary metabolites and proteins, including immunoglobulins. Interestingly, incubation with GOAT and particularly SHEEP saliva prompted the greatest fermentative activity in terms of gas production (+6%) and VFA concentration (+8%), as well as a greater bacterial abundance (+2%). The prokaryotic community composition in AUT incubators was the most different across treatments. These differences were mostly caused by a greater abundance of Proteobacteria and Rikenellacea and lower of Prevotellaceae, a key rumen bacteria with greater abundance in GOAT and SHEEP. These results indicate that the specific salivary components across species and individuals have moderate and distinct effects on the rumen microbiota.