Ruminal Planktonic, Weakly, and Tightly Feed-Adhered Bacterial Community As Affected By Two Trichoderma Reesei Enzyme Preparations Fed to Lactating Cattle

The objective was to compare effects of 2 T. reesei enzyme preparations (EFE) on the ruminal planktonic (LIQ) or the weakly (ASO) or tightly (SOL) feed-adhered ruminal bacterial community (fractions; FRC) of lactating dairy cows. The xylanase activities of the moderate (MIX) and high-xylanase (XYL) EFE tested were 10,549 and 26,926 μmol/min per g, respectively and both improved milk production from a dairy cow diet in a previous study. Three ruminally cannulated dairy cows (159 ± 47 DIM) were assigned to Control (CON), MIX or XYL treatments in an experiment with a 3 × 3 Latin square design with 23-d periods. The MIX and XYL EFE were sprayed on the TMR just before feeding at rates of 3.4 and 1 mL/kg of DM, respectively. Bacterial diversity was determined using the 16S rRNA gene (V1-V3 region) and the Illumina MiSeq platform. The data were analyzed with a model that included effects of EFE, FRC, their interaction and random effects of cow and period. The XYL increased (P < 0.05) relative abundance (RA, %) of Paraprevotellaceae (5.06 vs. 3.69±0.81), Spirochaetaceae (4.25 vs. 2.46±0.48) and tended (P = 0.11) to increase those of Prevotellaceae (31.8 vs. 24.09±2.82) versus the CON. The MIX decreased (P < 0.05) RA of Ruminococcaceae (4.61 vs. 9.09±2.23) and unidentified Clostridiales (4.48 vs. 6.61±1.43), and tended to increase (P = 0.06) that of Succinivibrionaceae (1.91 vs. 0.55±3.43) versus the CON. The SOL had higher RA (P < 0.05) of Lachnospiraceae (13.1 vs. 5.93±1.86), Veillonellaceae (8.49 vs. 3.22±1.69), unidentified Clostridiales (6.96 vs. 3.53±1.43), and Spirochaetaceae (3.40 vs. 1.52±0.48) and lower RA for unidentified Bacteroidales (3.48 vs. 9.96±1.49) versus LIQ. The XYL and MIX EFE only tended to reduce the RA of Veillonellaceae versus that of CON (6.30 and 5.30 vs. 13.9±2.54) in SOL (FRC × EFE; P = 0.07). The MIX EFE had lower phylogenetic diversity versus XYL and CON (48.6 vs. 51.6 and 51.2±1.47; P = 0.03). The weighted UniFrac distance showed only community structure differences between FRC (P < 0.01). Both XYL and MIX modified the bacterial community profile and diversity of the rumen fractions.