Strategic Addition of Different Additives to Improve Silage Fermentation, Aerobic Stability and In Vitro Digestibility of Napier Grasses at Late Maturity Stage

Napier cultivars are widespread in the tropics. To effectively prepare two Napier grasses at the late maturity stageas silage for ruminant feedstock, the silage fermentation characteristics, aerobic stability, in vitro digestibility, and gas kinetics were studied. Napier Pakchong grass (NP) and sweet grass (SG) were harvested at 120 dof regrowth and untreated (control) or treated with normal or a double dose of cellulase, urea, and formic acid. After 30 d of ensiling, the pH values of silages (ranging from 3.91 to 7.79) were affected ( p < 0.05) by additives and lower in control and cellulase-treated silages than in urea- and formic acid-treated silages. Adding cellulase resulted in greater lactic acid concentrations in SG silage. Adding urea boosted acetic acid, propionic acid, butyric acid, and ammonia nitrogen levels of silages. Adding formic acid spoiled silages and shortened the aerobic stability of NP silage. Compared with the control, the addition of cellulase at a double dose enhanced in vitrodry matter digestibility, and the gas production kinetics parameters of silages. Taking silage fermentation quality and in vitro dry matter digestibility into consideration, adding cellulase (0.2 g/kg fresh matter) to Napier grasses at the late maturity stage could be a better option compared with the other additives.