For the first time, Lactobacillus plantarum strains carrying heterologous genes encoding multifunctional glycoside hydrolases were constructed and used as additives for alfalfa silage. The chemical characteristics, nonstructural carbohydrate composition, and fermentation quality of alfalfa silage were examined. The supernatant of L. plantarum expressing CbXyn10C and Bgxg1 (LP11AG) showed activities on xylan, Avicel, and carboxymethylcellulose (CMC), while the supernatant of the wild-type L. plantarum showed no activity. When LP11AG was used as silage additive, the water-soluble carbohydrate content of alfalfa silage increased by 72%, 55%, and 155% compared with control when the silage was stored at 20 degrees C, 30 degrees C, and 40 degrees C, respectively. With LP11AG being used as an additive for the alfalfa silage stored at 20 degrees C, the hemicellulose, cellulose, and acid detergent ligninin (ADL) contents decreased by 17%, 6%, and 14% compared with the control (p < 0.05), respectively. Compared with the corresponding original contents, the contents of glucose, arabinose, galactose, and fructose detected in silage treated with LP11AG after 45 days of ensiling increased by 55%, 1494%, 68%, and 5% , respectively, when stored at 40 degrees C. Raffinose and stachyose, originally present in alfalfa, disappeared after ensiling. In conclusion, our results suggest that LP11AG provides a substantial benefit as a silage additive.