Effects of tannin-tolerant lactic acid bacteria in combination with tannic acid on the fermentation quality, protease activity and bacterial community of stylo silage.

Abstract

Proteolysis during ensiling primarily occurs due to undesirable microbial and plant protease activities, which reduce the protein supply to ruminant livestock and cause a series of environmental problems. The objective of this study was to investigate the effects of the tannin-tolerant lactic acid bacterium strain Lactiplantibacillus plantarum 4 (LABLP4) in combination with tannic acid (TA) on protein preservation in stylo (Stylosanthes guianensis) silage. The stylos were either ensiled without additives (control) or treated with LABLP4 (106 colony-forming units per gram of fresh matter), 1% (fresh matter basis) TA, 2% TA, LABLP4 + 1% TA and LABLP4 + 2% TA. Fermentation quality, protein composition, protease activity and bacterial diversity were determined at 3, 7, 14 and 31 days of ensiling. The combination of LABLP4 and TA decreased the pH, coliform bacteria count, non-protein nitrogen, ammonia-nitrogen (NH3-N) content and protease activities (P < 0.05) and increased the true protein content (P < 0.05) compared to the control. LABLP4 + TA led to a lower pH and NH3-N content than LABLP4 or TA alone (P < 0.05). On the last day (31 days) of ensiling, LABLP4 + TA increased the relative abundances of Firmicutes and Lactiplantibacillus (P < 0.05), except for the LABLP4 treatment, and decreased the relative abundance of Actinobacteria (P < 0.05). The combination of tannin-tolerant LABLP4 and TA effectively improved the fermentation quality of stylo silage and reduced protein degradation by altering the bacterial community structure. © 2024 Society of Chemical Industry.