Influence of season and diet on fiber digestion and the bacterial community in the rumen of muskoxen (Ovibos moschatus). MuskOxen rumen bacterial diversity

We studied the relationship between fiber digestion and the composition of the bacterial community in the rumen of muskoxen at the start and the end of the annual window of plant growth from spring to fall. Eight ruminally-cannulated castrated males were fed brome hay or triticale straw (37.8 vs. 52.2% lignocellulose respectively) that were similar in quality to the sedges consumed by wild muskoxen. Muskoxen digested fiber from both forages faster and to a greater extent when straw rather than hay was consumed. Fiber digestion was therefore inducible by diet in each season. We used sequences of 16sRNA from ruminal contents to study how season and diet affected the bacterial community, and how the latter related to fiber digestion. We found that Bacteriodetes and Firmicutes accounted for 90% of the sequences at the level of Phylum, which is typical for the gut microbiome. However, 35% of the genera identified were novel to the digestive system or related environments and may be a consequence of the evolutionary isolation of muskoxen. Between 48 and 72% of the variation in fiber digestion was associated with 36 – 43 genera of bacteria. Main fibrolytic bacteria typical of domestic ruminants were generally not among the most important bacteria associated with fiber digestion in muskoxen. Muskoxen rely upon on a large and novel suite of bacterial genera to digest the cell walls of plants that vary widely in both abundance and nutritional quality through the year.