Effects of additives on the fermentation and microbial quantity of legume-grass mixtures silage

This study aimed to investigate the effects of additives on the fermentation quality, protein degradation, and microbial quantity of legume-grass mixtures silage by utilizing the mixed grassland of Onobrychis viciifolia and Bromus inermis from the Ili Zhaosu Horse Farm, which had been established for an extended period. Two mixed grasslands with different growth conditions were selected, and their carbon-to-nitrogen ratios were determined as D₁: C/N 6.46 ꞉ 1 and D₂: C/N 11.12 ꞉ 1. A control group and three types of composite bacterial treatments were set up accordingly. The fermentation quality, nutritional composition, nitrogen fraction, protein fraction, tannin content, and microbial populations of the mixed silage were assessed after 30 days of silage fermentation. The protease activity of the mixed silage was dynamically measured at days 1, 3, 5, 14, and 30 of the fermentation process. The results indicated that the addition of the compound bacterial agent increased the lactic acid content, lowered the pH value and ammoniacal nitrogen content, elevated the levels of crude protein and soluble sugars, and minimized protein loss in the bean and grass mixed storage feeds. The additive also reduced protease activity and decreased the levels of non-protein nitrogen (PA) and bound protein (PC) in the mixed silage of legume and grass. It increased the levels of rapidly degradable protein (PB₁) and slowly degradable protein (PB₃), thereby reducing protein degradation. During the silage fermentation, the number of molds in each treatment did not exceed 2 log₁₀ cfu·g⁻¹. As the silage fermentation progressed, the populations of lactic acid bacteria and yeast initially increased and then decreased. The addition of additives increased the number of lactic acid bacteria and decreased the number of yeast in the legume-grass mixtures silage, with the A₁ additive presenting the most significant effect.