Bloat-associated dynamics of rumen bacterial and fungal communities

Frothy bloat is major digestive disorder of cattle grazing alfalfa pastures. Among the many factors identified to contribute to the development of frothy bloat, the disruption of rumen microbiota appears to be of central importance. Anaerobic rumen fungi (ARF) play an important role in sequential breakdown and fermentation of plant polysaccharides, thus serving as extensions of bacterial biofilms. In the present study, we investigated the dynamics of ARF during development of alfalfa-induced frothy bloat and in response to bloat preventive treatments. By sequencing the ITS1 region of metagenomic DNA from solid fraction of the rumen content, we were able to identify 8 distinct genera of the ARF. By performing correlation network analysis among the proportion of ARF and ruminal bacterial communities, we were able to identify hub fungi species that showed considerable number of negative correlations with several bacterial species, suggesting the presence of inter-kingdom competition between these two major groups of rumen microorganisms.