Lycium barbarum Residue Enhances Fermentation Quality and Antioxidant Activity of Alfalfa Silage

This study explored the potential application of Lycium barbarum residue (LBR) in alfalfa silage, particularly focusing on its synergistic effects when combined with silage additives. Two controlled experiments were conducted. In Experiment 1, four treatment groups were established with different LBR addition levels (0, 70, 140, 210 g/kg fresh weight, FW). Experiment 2 used the optimal LBR level identified (210 g/kg FW), and further investigated the effects of additive combinations. The treatments in this experiment included: (1) 210 g/kg FW LBR (CK), (2) a combination of 210 g/kg FW LBR with lactic acid bacteria (ALL), (3) a combination of 210 g/kg FW LBR with molasses (ALM), and (4) a combination of 210 g/kg FW LBR with both lactic acid bacteria and molasses (ALLM). The silage was ensiled for 7, 15, 30, and 90 days. The results demonstrated that the incorporation of LBR significantly enhanced silage fermentation quality. The 210 g/kg treatment exhibited the most favorable outcomes, characterized by the lowest pH, reduced ammonia nitrogen content, and the highest concentration of lactic acid. Additionally, 210 g/kg treatment showed increased levels of total phenolics and flavonoids, as well as enhanced antioxidant activities as measured by DPPH (2,2-diphenyl-1-picrylhydrazyl radical scavenging activity), ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity), and FRAP (ferric-reducing antioxidant power) assays. These improvements in bioactive compounds were positively correlated with lactic acid content and negatively associated with pH. Furthermore, in Experiment 2, the combined application of LAB and molasses along with LBR further optimized the silage quality, resulting in the lowest pH and ammonia nitrogen content, alongside a marked improvement in antioxidant capacity during the later ensiling stages. Overall, the study concludes that the inclusion of 210 g/kg LBR in combination with lactic acid bacteria and molasses effectively enhances both the fermentation process and the functional value of alfalfa silage, providing a scientific foundation for the utilization of agricultural byproducts.