Apple pomace addition improves fermentation quality, nutritive value and bacterial community succession of alfalfa silage.

OBJECTIVE: This study aimed to investigate the effects of apple pomace addition on the nutritional composition, fermentation quality, and bacterial community succession of alfalfa silage. METHODS: Alfalfa (357 g/kg fresh weight (FW)) was harvested at the early flowering stage and ensiled with no apple pomace (CK), 5%FW apple pomace (AL), and 10%FW apple pomace (AH) for 60 days at room temperature (23±1℃). The nutritional composition, fermentation quality, and bacterial community were analyzed. RESULTS: AH significantly improved silage quality compared with CK, evidenced by higher (P<0.05) lactic acid (28.41 vs. 15.24 g/kg DM), acetic acid (6.8 vs. 2.3 g/kg DM), dry matter (498 vs. 358 g/kg FM), crude protein (193 vs. 154 g/kg DM), and water-soluble carbohydrates (57.7 vs. 45.1 g/kg DM), and lower (P<0.05) pH (3.75 vs. 4.81) and ammonia nitrogen (38.4 vs. 69.8 g/kg TN). At the phylum level, Pseudomonadota (35.94%) and Bacillota (64.06%) dominated CK, whereas apple pomace supplementation increased Bacillota to 87.78% and decreased Pseudomonadota to 3.93%. At the genus level, apple pomace boosted Weissella, Lactiplantibacillus, and Bacillus. AL was dominated by Weissella (42.65%) and Bacillus (95.91%), while AH was predominantly colonized by Weissella (38.89%), Lactiplantibacillus (20.04%), Levilactobacillus (10.53%), and Lacticaseibacillus (8.79%), forming a more diverse lactic acid bacteria consortium. Spearman correlation analysis showed that Lactiplantibacillus and Weissella were positively correlated (P<0.05) with lactic acid and nutritional parameters, and negatively correlated (P<0.05) with pH. Functional profiling indicated that apple pomace reshaped metabolic functions and upregulated enzymes related to carbohydrate degradation, energy metabolism, and substrate transport, promoting lactic acid accumulation. CONCLUSION: Apple pomace enhanced fermentation performance and nutrient retention in alfalfa silage, and a 10% inclusion rate is recommended for practical production.