The effect of different additives on the fermentation quality, in vitro digestibility and aerobic stability of a total mixed ration silage

• L. plantarum was effective in improving fermentation of TMR silage.
• Ethanol showed a potential to protect TMR silages from aerobic spoilage.
• L. plantarum + ethanol ensure good fermentation and improve aerobic stability.

Fermented total mixed ration (TMR) is novel feed for ruminants in Tibet. Studies were conducted to compare the effects of using microbial inoculants, molasses and ethanol on the fermentation quality, nutritive value and aerobic stability of TMR silage. TMR were ensiled in laboratory silos (5 L) and treated with (1) no additive (control), (2) ethanol (E), (3) molasses (M); (4) Lactobacillus plantarum (L); (5) ethanol + molasses (EM); (6) ethanol + L. plantarum (EL). Ethanol was applied at 25 ml/kg fresh weight (FW), molasses was applied at 30 g/kg FW, and L. plantarum was applied at 106 cfu/g FW. All silos were opened after 45 days of ensiling, three silos per treatment were used for fermentation quality study and 18 silos for aerobic stability test. After 45 days of ensiling, TMR silages treated with ethanol had highest pH (P < 0.05), inoculant with or without ethanol significantly (P < 0.05) increased lactic acid (LA) concentration, decreased pH and ammonia nitrogen (AN) compared with control. Butyric acid (BA) concentration in L, EM and EL silages were significantly lower (P < 0.05) than that of control. Ethanol significantly (P < 0.05) decreased the population of lactic acid bacteria (LAB), aerobic bacteria and yeast. Ethanol alone or in combination with molasses or inoculant improved aerobic stability of TMR silages, indicated by higher and more stable LA content, smaller rise in pH, aerobic bacteria and yeast count than silages without ethanol. The pH for EL and EM remained at 3.91–4.41, whereas that in control, M and L gradually increased to exceed 4.80 after 9 days of aerobic exposure. Aerobic bacteria and yeast counts in control, M and L silages were increased to significantly (P < 0.05) higher value than those of E, EM and EL silages after 9 days of aerobic exposure. These results indicate that ethanol played an important role in the inhibition of aerobic bacteria and yeast growth and improvement of aerobic stability of TMR silages.