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Effects of rumen hypomotility on microbial community composition.

D. Cavallini



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Effects of rumen hypomotility on microbial community composition.
A. Palmonari, D. Cavallini*, G. Canestrari, G. Buonaiuto, S. Speroni, L. Campidonico, F. Ghiaccio, A. Formigoni, L. Mammi. Department of Veterinary Sciences, University of Bologna Ozzano Emilia, Italy.

Sudden drop in rumination time is usually defined as rumen hypomotility (RH), and these events could be related to different causes (i.e., dietary changes, environmental stresses, digestive pathologies, oestrus, lameness). The objective of this study was to evaluate, in high producing cows, the changes in rumen microbiota due to RH. Eight lactating Holstein cows were fed an acidotic diet (75% concentrates) for 28 d, once moved from the group to tie-stall. Rumen content was sampled before the animals were moved (T-3), once in the tie-stall (T0), and after 14 and 28 d since the experimental diet was fed. Rumen fluid was collected using an esophageal probe, and the first 500 mL of liquid was discarded to avoid saliva contamination. DNA was extracted according to an existing protocol, quantified using a NanoDrop system. V3-V4 region of the 16S rRNA gene was amplified using 341F and 805R primers plus Illumina adapter, then sequencing was performed on Illumina MiSeq according to the manufacturer's instructions. Raw sequences were processed using a pipeline with PANDAseq, QIIME2 and DADA2. High-quality reads were clustered into high-resolution operational taxonomic units (OTUs). Using taxonomic assignment, OTU tables were collapsed from phylum to genus level. Alpha diversity was computed using OTUs, Shannon index and Faith's diversity metrics. Beta diversity was estimated by computing weighted and unweighted UniFrac distances into Principal Coordinates Analysis (PCA). Statistical analysis was performed using R. Significant differences in α or β diversity were assessed by Wilcoxon test. Overall, 4 animals underwent RH. Obtained results showed that animals with RH had a different microbial community composition compared with the others (P < 0.01), still maintaining a higher number of OTUs than animals reacting differently to the acidotic diet. Moreover, variability across samples at different time points was lower (P < 0.01) in RH animals compared with the others, showing higher consistency during the whole trial. In conclusion, rumen hypomotility impacted rumen microbial ecosystem, which showed several differences in respect to not affected animals.

Keywords: rumen hypomotility, rumen microbiota.