Ruminal Planktonic, Weakly, and Tightly Feed-Adhered Bacterial Community as Affected by Two Trichoderma reesei Enzyme Preparations Fed to Lactating Cattle

This study evaluates the effects of two Trichoderma reesei exogenous fibrolytic enzyme (EFE) preparations on the taxonomic profile, diversity, relative abundance, and population shifts of three ruminal bacteria fractions of lactating cows: free-floating (LIQ), weakly (AS), and tightly (SOL) feed-adhered. Three lactating cows were fed three EFE treatments in a 3 × 3 Latin square design: one control (CON) without enzymes, a cellulase/xylanase mix (MIX), and a high-xylanase treatment (XYL). Rumen contents were collected, and bacteria were extracted from the three ruminal content fractions for next-generation sequencing analysis. Alpha diversity was higher in XYL compared to CON. However, no EFE effect was observed on beta diversity. The relative abundance (RA) of the family Prevotellaceae increased, while that of Ruminococcaceae and Rikenellaceae decreased in XYL compared to MIX and CON. The bacterial community structure (beta diversity) of LIQ was differentiated from that of SOL and AS (p = 0.03), but no effects of fraction were observed on alpha diversity. Lachnospiraceae RA was greater in SOL, followed by AS, and lower in LIQ (p < 0.001), while Spirochaetaceae RA was greater in SOL and AS compared to LIQ (p = 0.003). The effects of EFE supplementation on rumen bacterial RA were independent of the ruminal content fraction.