High-moisture alfalfa silage fermentation: a comparative study on the impact of additives including formic acid, , cinnamon essential oil, and wood vinegar.

Applying additives to high-moisture alfalfa silage is crucial for ensuring fermentation quality. The study selected two conventional silage additives (formic acid [FA] and [LP]) and two additives with the potential to improve silage fermentation quality (cinnamon essential oil [CEO] and wood vinegar [WV]) as the subjects of the research, with the control group sprayed with an equal amount of distilled water (CK). We compared the fermentation products of high-moisture alfalfa silage at 3 d, 7 d, 15 d, 30 d, and 60 d with different additives and evaluated the dry matter (DM) digestibility, crude protein (CP) digestibility, and the bacterial community composition, co-occurrence network, function, and phenotype prediction of the alfalfa silage at 60 d of fermentation. The results indicate that after the application of additives, the pH of the alfalfa silage decreased more rapidly, and it retained more DM and CP, produced more lactic acid (LA), and reduced the levels of acid detergent fiber, neutral detergent fiber, acetic acid, and butyric acid, thereby enhancing DM digestibility and CP digestibility. In terms of bacterial community composition, LA bacteria are virtually absent in the CK group, with harmful microorganisms such as predominating. LP, CEO, and WV are enriched with a large number of bacteria beneficial to LA fermentation, such as , , , and . At the same time, the bacterial co-occurrence network structure tends to simplify, and it significantly reduces Potentially Pathogenic and Mobile Element Containing. In summary, LP, CEO, and WV are more effective additives for high-moisture alfalfa silage, capable of effectively improving the quality and safety of the silage.IMPORTANCEDuring the ensiling process of alfalfa, the growth and proliferation of harmful microorganisms can lead to a decline in silage quality. In this study, we report for the first time the improvement effect of cinnamon essential oil (CEO) and wood vinegar (WV) on the quality of alfalfa silage, which outperforms formic acid. This provides a reference for the development of novel silage additives. The results indicate that the addition of , CEO, and WV can enhance the abundance of beneficial microorganisms, including , , , and , while inhibiting the growth of harmful microorganisms such as , thereby effectively improving the quality and safety of alfalfa silage.