Effects of Lactobacillus plantarum and Saccharomyces cerevisiae on rumen fermentation parameters, microbial diversity and metabolites of fermented feed in vitro

The purpose of this study was to study the effects of Saccharomyces cerevisiae (SC) and Lactobacillus plantarum(LP) on rumen fermentation, rumen microflora and rumen microbial metabolism by using SC and LP to ferment crop processing by-products. Treatments were as follows:Control (fermented feed); SC group (Saccharomyces cerevisiae addition group); LP group (Lactobacillus plantarum addition group); SCLP group (Saccharomyces cerevisiae and Lactobacillus plantarum addition group). The treatment groups were subjected to in vitro rumen fermentation for 48 h using fermentation bags. The results showed that the addition of SC, LP and SCLP reduced the contents of neutral detergent fiber (NDF) and acid detergent fiber (ADF), and the crude protein (CP) content of SC and SCLP also increased significantly.The abundance of nutrient degrading bacteria such as Spirochaetota and Fibrobacterota in the rumen microbiota of the SCLP group increased, improving the digestion and absorption of nutrients. Compared with the CON, the metabolites of the Aminoacyl-tRNA biosynthesis pathway, Glycine, serine and threonine metabolism pathways, Protein digestion and absorption pathways were up-regulated, and the metabolites of vitamin digestion and absorption pathways and mineral absorption pathways were significantly up-regulated in the LP group and SCLP group.In conclusion, the synergistic effect of using Saccharomyces cerevisiae and Lactobacillus plantarum fermented feed can improve the nutritional level of fermented feed, regulate the rumen environment, and enhance the digestion and utilization of feed.