Effect of Distillery Spent Wash Utilization on Maize Silage Fermentation and In Vitro Methane Production

The animal husbandry industry is a major source of agricultural greenhouse gas emissions, and methods to reduce methane production from livestock during rumen fermentation are an important research issue. Distillery spent wash (DSW) is a by-product of the brewing industry, and to our knowledge, its application in feed processing has rarely been reported. This work investigated the effect of using DSW as an additive on silage fermentation and <i>in vitro</i> methane production. A small-scale silage production system for whole-plant maize was applied, and maize was treated without (control) and with DSW (G2, 10 mL·kg^-1 fresh matter (FM); G4, 20 mL·kg^-1 fresh matter). After 60 days of ensiling, the pH value of G2- and G4-treated whole-plant maize was reduced (<i>p</i> < 0.05), while lactic acid production was significantly enhanced to 3.40% DM for G2 and to 3.43% DM for G4, effectively improving silage fermentation. In fact, the addition of DSW shifted the bacterial community structure in whole-plant maize silage, significantly increasing the dominance of <i>Lactiplantibacillus</i> from 10.1% (CK) to 74.1% (G2) and 62.5% (G4) and thereby decreasing the diversity indices of silage samples. However, DSW application increased the ammonia-N levels in silage by 135.29-147.06% compared with the control. Importantly, there was a reduction of 0.70 and 0.55 percentage units in CK for G2 and G4, respectively, which represent 57.6% and 44.0% reductions in the acetic acid concentration, respectively, which were accompanied by a trend of decreasing methane production and <i>Methanobrevibacter</i> abundance. In conclusion, DSW exhibits potential for enhancing lactic acid fermentation by increasing <i>Lactiplantibacillus</i> and for inhibiting <i>in vitro</i> rumen methane production by promoting <i>Methanobrevibacter</i> dominance.