Effects of the Addition of Rumen Fluid and Molasses on the In Vitro Rumen Digestion Characteristics of Caragana korshinskii Kom. Silage

This study aimed to investigate the effects of molasses and rumen fluid addition on in vitro rumen fermentation, nutrient digestibility, and microbial community structure in Caragana korshinskii Kom. silage. The artificial rumen method was adopted to determine the in vitro rumen digestion indicators of four different kinds of silage: silage without additives (CK), silage with 7% rumen fluid (R), silage with 4% molasses (M), and silage with both 7% rumen fluid and 4% molasses (RM). Samples from each treatment were taken at days 15 and 60 to investigate the changes during ensiling. As for the 60-day silage, the rumen gas production and gas production from the insoluble but fermentable fraction were significantly lower in the R and RM groups than in the CK group (p < 0.05). Moreover, the methane production in the R group was the lowest. As for both the 15-day silage and 60-day silage, the M group exhibited a significantly higher gas production rate relative to the CK and R groups (p < 0.05). The digestibility of neutral detergent fiber and acid detergent fiber was significantly reduced in the M and RM treatments compared with the CK and R treatments. Conversely, the M and RM treatments had significantly lower propionate concentration but a significantly higher acetate-to-propionate ratio than the CK and R treatments (p < 0.05). R treatment exhibited greater relative Prevotella abundance than M and RM treatments (p < 0.05). In the 60-day silage, the M and RM treatments had higher Methanobrevibacter abundance but lower Methanosphaera abundance than CK treatment (p < 0.05). Silage with molasses reduced the dry matter, NDFD and ADFD, and reduced the total volatile fatty acids and the propionate content, but increased the A/P and CH4 production. In contrast, silage with rumen fluid had a relatively small impact on rumen TVFA, NDFD and ADFD, but increased the dry matter digestibility and reduced the GP and CH4 content.