Intrinsic tannins affect ensiling characteristics and proteolysis of Neolamarckia cadamba leaf silage by largely altering bacterial community.

The mechanism that tannins alter microbial community to inhibit proteolysis and enhance silage quality is unclear. Neolamarckia cadamba leaf (NCL; rich in tannins) were ensiled alone or with addition of polyethylene glycol (PEG, tannins inactivator), and then fermentation quality, proteolysis activity and bacterial community were investigated during ensiling (Day 3, 7, 14 and 30). As a result, PEG addition increased lactic acid (1.09% vs 2.03%, on dry matter basis) and nonprotein-N (13.65% vs 17.59%, on crude protein basis) contents but decreased ammonia-N content (9.21% vs 2.29%, on crude protein basis) in NCL silage. Meanwhile, the dominant microbiome shifted from Cyanobacteria (60.92%-81.50%) to Firmicutes (48.96%-88.67%), where the unclassified genus (80.95%-85.71%) was substituted by Leuconstoc (42.03%-55.55%) and subsequently Lactobacillus (65.98%-82.43%). This study suggests that the intrinsic tannins inhibit lactic acid fermentation and protein degradation in NCL silage.