The effectiveness of chemical additives on fermentation profiles, aerobic stability and in vitro ruminal digestibility of total mixed ration ensiled with Napier grass and wet distillers’ grains in southeast China

Chemical additives have been widely used to restrain the growth of undesirable microorganisms, and they were ideal additives to well preserve silages. The work aimed at evaluating the effects of four chemical additives on fermentation quality, aerobic stability and in vitro ruminal digestibility of the fermented total mixed ration (FTMR). The TMR was treated with: (1) no additive (control); (2) sodium diacetate; (3) calcium propionate; (4) sodium benzoate (SB); (5) potassium sorbate (PS) on a fresh weight (FW) basis. After 60 days of ensiling, the silos were opened and sampled to determine fermentation quality, in vitro rumen parameters, and then the 60-day FTMR were subjected to a 9-day aerobic stability test. Chemical additives significantly (p < 0.05) increased dry matter, crude protein, and water-soluble carbohydrates contents, and decreased ammonia nitrogen, ethanol contents, aerobic bacteria and yeast counts after 60 days of ensiling. During aerobic exposure, chemical additives obviously improved aerobic stability as indicated by higher lactic acid, water-soluble carbohydrates contents and lactic acid bacteria counts, and lower pH, ethanol, ammonia nitrogen contents, aerobic bacteria and yeast counts. Treatments with SB and PS had higher (p < 0.05) lactic acid content, and lower (p < 0.05) pH, ammonia nitrogen content, aerobic bacteria and yeast counts than other FTMR. After 72 h of incubation, chemical additives significantly (p < 0.05) increased cumulative gas production, in vitro digestibility of dry matter and crude protein. The SB and PS-treated FTMR had higher (p < 0.05) cumulative gas production and in vitro dry matter digestibility than other FTMR. These results indicated that SB and PS were more effective to improve aerobic stability and in vitro ruminal parameters, and they were recommended as optimal additives for FTMR.HIGHLIGHTS Four chemical additives were served as additives for fermentation total mixed ration Chemical additives markedly improved fermentation quality, aerobic stability and in vitro ruminal parameters Sodium benzoate and potassium sorbate were optimal for improving aerobic stability and in vitro parameter