Investigation of the effect of different additives on the qualities, in vitro degradation, and rumen fermentation profile of indigo waste silage

Natural indigo dye production produces indigo waste as a by-product. Our purpose of this study was to examine the effects of calcium hydroxide (Ca(OH)2), cellulase (CE), molasses (MO), and their combinations on the silage quality, in vitro degradability, and rumen fermentation parameters of indigo waste silage. A completely randomized design (CRD) was used for the experiment. Indigo waste was chopped and ensiled in a small-scale silo with no additive (control), Ca(OH)2, MO, CE, Ca(OH)2:MO, Ca(OH)2:CE, MO:CE, and MO:CE:Ca(OH)2. After 30 days of storage, the silages were tested for quality and chemical composition, as well as an in vitro fermentation. The ruminal fluid inoculum was collected from two beef cattle with a body weight (BW) of 200±10 kg, and the inoculum had been pre-heated before being transported to the laboratory. Silage with MO, CE, or their combination increased the amount of lactic acid (p < 0.01). The silage pH was lowest in MO:CE (4.5) and was highest in Ca(OH)2:CE (10.6) in indigo waste (p < 0.01). In comparison to the control (19.5% CP), the CP content of all additives increased by 20.7% to 21.5% (p = 0.02). The addition of Ca(OH)2:MO and Ca(OH)2:CE resulted in a reduction of NDF content by 60.7% and 59.4%, respectively, in comparison to the control group (72.4%) (p < 0.01). Silage with additives had no effect on the cumulative gas production or gas kinetics, except that the constant rate of gas production for the insoluble fraction (c) was higher in MO (p = 0.03). In vitro dry matter degradability (IVDMD) was higher in CE and MO and highest in MO:CE-treated silage (p < 0.01). The in vitro organic matter degradability (IVOMD) increased in Ca(OH)2:MO compared with the control (p = 0.03). The additives alone or in their two combinations in silage reduced the ruminal ammonia-nitrogen (NH3-N) concentration (28.0 to 31.5 mg/dL) when compared to the control (32.7 mg/dL) (p < 0.01). In addition, the highest total volatile fatty acid (VFA) level was found in the silage of the MO (92.9 mmol/L) compared with the control (71.3 mmol/l) (p < 0.01). The proportion of propionic acid and butyric acid increased (p < 0.01) whereas acetic acid decreased (p < 0.01) in the rumen of silage with MO and CE. In summary, the addition of MO and CE has the potential to be used in the silage of indigo waste.