Effect of different biological probiotics on the quality of cassava root silage and the impact on microbial flora diversity

We performed an experiment using fresh cassava root (South China No. 9) tubers under four different treatments: microbial fermenting agent (C₁), high efficiency complex bacterial enzyme preparation (C₂), biological feed fermenting agent (C₃), and the control group (CK), with equal volumes of distilled water. The nutrient composition, fermentation quality, and microbial community structure were measured after 30 days of closed fermentation after the tuber material and bacterial agent were thoroughly mixed. The objective was to discover the effect of adding different biological probiotics on silage quality and microbial diversity of cassava tubers.The results showed that the dry matter and lactic acid content were significantly elevated in each treatment group after the addition of bio-probiotics (P < 0.05), and there were no significant differences in soluble sugars, neutral detergent fiber content, and lactic acid/acetic acid (P > 0.05). The crude protein content of the C₂ group was significantly lower than that of the CK group(P < 0.05). The acid detergent fiber content was significantly lower in the C₁ and C₃ groups than in the CK group (P < 0.05). The level of acetic acid in the C₁ group was significantly higher than that in the CK group (P < 0.05). The pH of all four treatment groups was below 4.2; a small amount of propionic acid was detected, but no butyric acid was detected, and ammoniacal nitrogen/whole nitrogen was below 10% in all the treatment groups. It shows that the four treatment groups are of excellent quality. The microflora structure was then analyzed and we found that the abundance, diversity, and uniformity of distribution of the flora were reduced. At the phylum level, the addition of bioprobiotics resulted in a significant increase in the abundance of the thick-walled phylum (P < 0.05), and a significant decrease in the abundance of the cyanobacterial phylum, unclassified bacteria, and other bacteria (P < 0.05). Among them, the phylum Proteobacteria was significantly reduced in group C₃ (P < 0.05). At the genus level, the addition of bio-probiotics increased the abundance of dominant genera, such as Lactobacillus and Lactococcus and decreased the abundance of miscellaneous bacteria, such as unclassified Enterobacter and Serratia. The combined analysis showed that the effect of adding different biological probiotics to cassava tubers was C₃ > C₁ > C₂.