Effects of tea leaf waste of green tea, oolong tea, and black tea addition on sudangrass silage quality and in vitro gas production

This study evaluated the fermentation characteristics and in vitro gas production of sudangrass (Sorghum sudanese) silage with tea leaf waste of green tea, oolong tea and black tea added. All types of tea leaf waste contain large amounts of nitrogen (N) and tannins, and a small amount of lowwater-soluble carbohydrates. Sudangrass was preserved without (control) and with green tea waste (GTW), oolong tea waste (OTW) or black tea waste (BTW) at rates of 50, 100 and 200 g kg^-1 fresh matter in laboratory silos. The pH and butyric acid levels were significantly lower in GTW at all rates and in OTW at the 200 g kg^-1 rate, whereas those levels were high in the control and BTW-treated silage. Lactic acid level was appreciably higher in GTW- and OTW-treated silage than the control and BTW-treated silage. The addition of all types of tea waste increased the total N and tannins of the silage, whereas the acid detergent insoluble N was increased in the OTW- and BTW-treated silage. GTW treatment increased gas production within a 96-h period compared with the control, whereas OTW and BTW additions at 200 g kg^-1 rates caused lower gas production. It is concluded that the fermentation characteristics and feed value of the silage incorporating with tea leaf wastes are different for these types of tea leaf. Among the three kinds of tea waste, GTW is the most valuable material as a silage additive.