Effect of 4‐Pentenoic Acid and Malic Acid on Dynamics of Bacterial Community and Fermentation Characteristics in Nettle Silage

[Background] Nettle is a potential non-conventional feed resource due to its high level of crude protein content, and ensiling is better for utilization in the animal industry. Previous integrated analysis (microbiome and metabolome) suggested that 4-pentenoic acid and malic acid in ensiled nettle may inhibit harmful microorganisms within the system. The present study investigated the effects of these two acids on nettle silage quality through the addition of 1% fresh weight of these acids then analyzed the characteristics and bacterial community during 60 days of nettle ensiling. [Results] Addition with 4-pentenoic acid increased the content of crude protein (CP) and acetic acid (AA) when compared with both control and malic acid treated during 30 to 60 days of ensiling (p＜0.05). Lactic acid (LA) content was highest in malic acid treated (4.21 %, dry matter, DM based) when compared with control and 4-pentenoic acid treated after 7 days of nettle ensiling (p＜0.05), but lower when compared with 4-pentenoic acid treated after 30 days of nettle ensiling (p＜0.05), and was not detected in all groups after 60 days of silage. The content of butyric acid (BA) and ammonia (AN) was lowest (2.92%—4.39% of DM and 9.94 % —24.28% of total nitrogen, respectively) in 4-pentenoic treated when compared with both control and malic acid treated during 30 to 60 days of ensiling (p＜0.05). Both acids treated increased relative abundance of Weissella after 30 days of nettle ensiling, especially for 4-pentenoic acid showed the higher capacity. Both acids treated showed trend to inhibited relative abundance of Clostridium sensu stricto 15 after 30 days of nettle ensiling. Clostridium sensu stricto 15 showed significant positive correlation with BA and AN (p＜0.05). [Conclusion] Present study results suggested that addition of 4-pentenoic could improve quality of silage due to reduction level of protein degradation probably resulting from its inhibited activity against to Clostridium spp. However, malic acid was less effective than 4-pentenoic acid in suppressing Clostridium spp. activity and the associated production of BA and AN, resulting in inferior preservation of CP.