From Formulation Screening to Animal Performance: Optimizing Miscanthus Ensiling Strategies for Enhanced Rumen Fermentation and Growth in Sheep

Miscanthus exhibits a high annual dry matter yield and favorable nutritional profiles during its vegetative growth stage, making it well-suited for ensiling and as a high-quality roughage resource for ruminants. This study investigated the effects of fermentation with different lactic acid bacteria combinations on the quality of miscanthus ensiling, as well as the impact of replacing corn straw silage with varying proportions of miscanthus silage on the growth performance, rumen fermentation, and rumen microbiota of sheep. The results revealed that the LP2 and CB groups exhibited higher contents of dry matter, crude protein, and lactic acid than the other groups at the end of the ensiling period. Moreover, throughout the entire ensiling period, the LP1 and LP2 groups demonstrated lower ratios of ammonia-nitrogen/total nitrogen, lower acetic acid contents, and higher LA/AA ratios. 16S rDNA sequencing revealed that during the mid and late fermentation stages, the LP1 and LP2 groups maintained higher microbial diversity, greater relative abundance of beneficial bacteria, and higher expression levels of genes related to microbial metabolism and biosynthesis pathways of secondary metabolites. In the feeding trial, compared with the CON group, the MS50 group significantly increased average daily gain and dry matter intake, and significantly elevated ruminal ammonia N concentration. Both the MS50 and MS100 groups significantly improved the apparent digestibility of crude protein and acid detergent fiber. Analysis of differentially abundant bacteria indicated that the rumen of sheep in the MS50 and MS100 groups had a higher relative abundance of fibrolytic bacteria but a lower relative abundance of bacteria involved in carbohydrate fermentation. KEGG pathway analysis suggested that the microbiota in the MS50 group prioritized fiber degradation, while the MS100 group potentially enhanced energy balance and improved energy utilization efficiency by upregulating cobalamin transport. CAZyme results demonstrated that miscanthus silage likely enhanced microbial degradation of plant cell wall fiber components by downregulating glycoside hydrolase (GH) family genes and upregulating glycosyltransferase (GT) and carbohydrate binding module (CBM) family genes, thereby meeting the energy demands of the animals. In conclusion, using Lactiplantibacillus plantarum LW8 and K3 at a 2:1 ratio for a 40-day ensiling period achieved the optimal silage quality in miscanthus. Furthermore, substituting 50% of corn straw silage with miscanthus silage resulted in the most favorable feeding outcomes.