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Characterization of the dairy cow rumen epimural microbiota under high-forage and high-starch diets.

D. Sbardellati



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Characterization of the dairy cow rumen epimural microbiota under high-forage and high-starch diets.
D. Sbardellati*1, A. Fischer2, K. Kalscheur2, G. Suen1. 1Department of Bacteriology, University of Wisconsin-Madison Madison, WI, 2USDA Dairy Forage Research Center, USDA-Agricultural Research Service Madison, WI.

The ruminal microbial communities of dairy cattle are crucial for providing nutrition from otherwise host-inaccessible dietary components. The majority of rumen microbiological research has focused on communities associated with luminal solids and liquids. However, a third microbiota is found closely associated with the ruminal epithelium (the epimural microbiota). This epimural community serves an important role as the interface between the host and its symbiotic community. Despite its functional importance, there is little research exploring the epimural microbiota within the context of diet and energy harvest in dairy cows. Diet has been shown to alter luminal microbial communities, but how epimural communities respond to similar changes in diet is less well understood. To explore this, we used next-generation 16S rRNA sequencing to characterize the bacterial community associated with the epimural tissue of 13 lactating Holstein dairy cows fed high-starch (diet A) and high-forage (diet B) diets. A diet-crossover experimental design consisting of 2 groups, 2 diets, and 2 sampling periods, was used. Animals were randomly assigned to 2 diet-transition groups (A-B, n = 6; B-A, n = 7). Groups received a single diet for 8 weeks, followed by a 10-d transition period and a final 8-week diet-treatment. All epithelial samples were collected at the end of each 8-week period. Rumen epithelial tissue was collected from the ventral sac after partial rumen evacuation. Under both diets, bacterial communities were characterized by high abundances of operational taxonomic units (OTUs) from the phyla Firmicutes, Bacteroidetes, Proteobacteria, Epsilonbacteraeota, and Spirochaetes. Our results suggest that diet did not significantly impact epimural community richness (Chao's richness; P > 0.10) or diversity (Shannon's diversity; P > 0.10). However, we found that diet-treatment led to bacterial communities significantly different in structure (Bray-Curtis; PERMANOVA P < 0.05) and composition (Jaccard; PERMANOVA P < 0.05). Of the OTUs which changed in abundance according to diet, an OTU classified to the family Succinivibrionaceae increased in abundance under a high starch diet (P < 0.05) while another OTU classified to the order Bacteroidales increased in abundance under a high fiber diet (P < 0.05). These diet-dependent differences in epimural microbial community likely have important consequences for host energy harvest and general health.

Keywords: rumen, epimural, microbiota.

Biography: My name is Dino Sbardellati. I obtained my BA in Biology from Sonoma State University where I studied the ecological impacts of reintroduced, endemic, Tule elk. I am currently a MS student in the lab of Dr. Garret Suen at the University of Wisconsin-Madison. Here I have been studying the bacterial communities associated with the epithelial tissue of Holstein dairy cows.