Effect of different levels of corn steep liquor addition on fermentation characteristics and aerobic stability of fresh rice straw silage

The object of this study was to determine the proper mixing ratio of fresh rice straw to corn steep liquor (CSL) to obtain a high protein content silage feed. The following experimental silages were generated: the control (C1), composed of fresh rice straw without CSL additive, mixed with CSL in the ratios of 4:1 (C4), 3:1 (C3) and 2:1 (C2). Lactic acid bacteria (LAB) inoculant was applied at the rate of 50 mL/kg (fresh basis) of forage to achieve a final application rate of 1 × 106 cfu/g of fresh matter (FM). Duplicate silos for each treatment were opened after 0, 3, 7, 10, 20, 30, 45 and 60 d for microbiological and chemical analysis. The results showed that the addition of CSL significantly increased crude protein (CP) contents, and decreased neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents of treatments after 60 d of ensiling (P < 0.05). The lactic acid contents in C4 and C3 were significantly higher than that in C1 (P < 0.05). In summary, mixing fresh rice straw with CSL at addition levels of 4:1 (C4) and 3:1 (C3) can improve the fermentation quality and nutrient composition of fresh rice straw silage. However, a large proportion of CSL (C3) had a negative impact on the aerobic stability of fresh rice straw.