Effects of a compound microbial agent on mixed silage quality of Alhagi sparsifolia and Sorghum bicolor

In this study, in vitro gas production method was used to analyze the effects of a compound microbial agent on silage quality of Alhagi sparsifolia mixed with Sorghum bicolor. Alhagi sparsifolia and Sorghum bicolor. were mixed for silage according to raw material fresh weight ratios of 10:0, 7:3, 5:5, 3:7, and 0:10. An additive-free group (an equal amount of distilled water) and a compound microbial agent group (Lactiplantibacillus plantarum, Lactobacillus brucei, Heyndrickxia coagulans, and Bacillus subtilis) of 0.02 g·kg⁻¹ were established for each mixing ratio. Samples were collected after 60 days of fermentation for the in vitro fermentation test. Results showed that the theoretical maximum gas production, 48 h gas production, and gas production rate of the compound microbial agent group were higher than those of the additive-free group (P < 0.05). As the proportion of S. bicolor in fermentation substrate increased, the contents of acetic acid, propionic acid, and butyric acid in the fermentation broth showed an increasing trend, while ammonia nitrogen content decreased (P < 0.05). Dry matter digestibility, crude protein digestibility, neutral detergent fiber digestibility, and acid detergent fiber digestibility were higher in the compound microbial agent group than in the additive-free group (P < 0.05). Through comprehensive analysis using the affiliation function method, it was revealed that the best rumen fermentation effect occurred when the mixing ratio of A. sparsifolia and S. bicolor was 3:7, with supplementation of the compound microbial agent.