Application of tannins in mulberry silage: Reducing protein degradation during silage and rumen fermentation

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Mulberry ( Morus alba L.), a high-protein woody forage, has considerable potential to alleviate protein feed shortages in animal husbandry. However, its utilization is constrained by substantial protein degradation during anaerobic fermentation and ruminal digestion. This study investigated the effects of tannic acid (HT) and Acacia mangium tannin (CT) at five graded inclusion levels (1, 2, 3, 4 and 5 g/kg dry matter, DM), together with a control treatment (CK), on the fermentation quality, bacterial community composition and protein utilization of mulberry silage after 60 days of ensiling, with four independent biological replicates per treatment. The results showed that HT dose-dependently reduced crude protein loss during fermentation, with a maximum reduction of 2.72% compared with the control. HT also promoted the dominance of Lactiplantibacillus , suppressed undesirable microorganisms, and optimized silage protein profiles by elevating PB2 and PB3 fractions and reducing non-protein nitrogen (NPN), which is poorly available to ruminants and leads to protein resource waste, increased urinary nitrogen excretion and associated environmental pollution risks. In contrast, CT promoted protein degradation during fermentation and suppressed the abundance of Lactiplantibacillus . Both tannin sources decreased ruminal protein degradation, with reductions of up to 17.94% (add 5 g/kg tannic acid). These findings reveal the regulatory mechanisms of tannins on microbiota and protein degradation in mulberry silage. Amid surging ruminant feed demand and severe environmental pressures from conventional grain feeds, this study lays a theoretical basis for promoting mulberry as sustainable ruminant forage with higher nutrient utilization. It also delivers a viable technique to mitigate silage nitrogen loss and lower nitrogen pollution from ruminant production.