Evaluation of gallnut tannin and Lactobacillus plantarum as natural modifiers for alfalfa silage: Ensiling characteristics, in vitro ruminal methane production, fermentation profile and microbiota

The potential of gallnut tannin (GT) and Lactobacillus plantarum (LP) on fermentation characteristics, in vitro ruminal methane (CH4 ) production and microbiota of alfalfa silage was investigated.Alfalfa was ensiled with GT (20 and 50 g kg-1 dry matter [DM]) and LP (3 × 108 CFU per gram fresh matter) alone or in combination for 60 days. The GT and LP alone or in combination decreased DM losses, pH and non-protein nitrogen contents of alfalfa silage. All additive treatments decreased ruminal CH4 production, and increased propionic acid molar proportions and Fibrobacter succinogenes numbers. The LP treatment increased nutrient degradation, cellobiase, pectinase and protease activities, and Prevotella ruminicola abundance, whereas high-dose GT treatment inhibited these variables. Importantly, LP together with GT alleviated the adverse effects of high-dose GT supply alone by enhancing pectinase and protease activities as well as Rumincoccus flavefaciens and P. ruminicola growth.Combination of GT and LP can be used as an efficient additive to improve silage quality and utilization by ruminants.Using GT-LP combination has practical implications, particularly concerning effects of tannins on ruminal CH4 mitigation, which may alleviate inhibitory effects of tannins on feed digestion through modulating ruminal microbiota.