Citric Acid Influences the Dynamics of the Fermentation Quality, Protease Activity and Microbial Community of Mulberry Leaf Silage

Abstract

Mulberry (Morus alba) leaves has performed well as a high-quality protein supplement for livestock and enriches the edible resources of livestock. However, the harvest of mulberry leaves is seasonal and occurs mainly during the rainy season in southeast China; therefore, humid and sultry weather causes serious losses of mulberry leaf biomass, which pose a challenge for the preservation of mulberry leaves. In this study, we used the silage fermentation method to preserve mulberry leaves and investigated the effects of citric acid on the silage quality of mulberry leaves. Mulberry leaves were ensiled with or without 1% citric acid and 2% citric acid. The chemical composition, protein fraction and microbial community of mulberry leaf silages were analyzed. The results showed that the silage treated with citric acid had a higher dry matter recovery and lactic acid content and a lower acetic acid content, non-protein nitrogen content and ammonia-N content; citric acid also inhibited the activities of carboxypeptidase and aminopeptidase. Moreover, citric acid increased Lactobacillus abundance in silages and decreased the abundance of undesired microorganisms, such as Enterobacter. In summary, the addition of citric acid improved the fermentation quality of mulberry leaf silages, with 2% citric acid being more effective than 1% citric acid.

Keywords

• mulberry leaves
• silage
• citric acid
• fermentation quality