Harvest Stage Dictates the Nutritive Value of Sorghum Stalk Silage by Shaping Its Fermentation Profile and Microbial...

The present experiment aimed to investigate the effects of harvest stages on the fermentation quality and nutritional value of sorghum stalk silage. Sorghum stalks were harvested at the three stages (milk, dough, and ripe), chopped, and ensiled for 60 d. Each treatment had five replicates, and the silages were evaluated for fermentation quality, nutritional composition, in vitro rumen fermentation characteristics, and bacterial community profiles. The results showed that the crude protein, neutral detergent fiber, and acid detergent fiber contents decreased significantly with harvest maturity (p < 0.05). Consequently, silage from the ripe stage possessed the highest dry matter, relative feed value, and total digestible nutrients (p < 0.05). In vitro rumen fermentation indicated that the ripe stage silage exhibited the greatest gas production, and the lowest concentrations of ruminal ammonia-nitrogen (p < 0.05). Microbial analysis revealed a shift from dominant epiphytic Proteobacteria to fermentative Firmicutes post-ensiling, with the ripe stage community co-dominated by Lactobacillus and Leuconostoc, in contrast to the milk stage's enrichment with Klebsiella. In conclusion, harvesting sorghum at the ripe stage is the optimal strategy as it establishes a beneficial microbial community, resulting in silage with superior nutritional value and rumen fermentation efficiency.