Ensiled Pleurotus ostreatus based spent mushroom substrate from corn: In vitro gas production, greenhouse gas emissions, nutrient degradation, and ruminal fermentation characteristics.

The present study evaluated varying inclusion levels (10%, 20%, 30%, 40%, and 50%) of spent mushroom substrate (SMS) derived from Pleurotus ostreatus, ensiled for 0, 21, 42, and 64 d, using an in vitro batch culture technique. The study employed a 6 × 4 factorial design with six inclusion levels and four ensiling durations. The batch culture was conducted over 24 h across two runs. Gas production (GP), greenhouse gases (GHG) production, nutrient degradability, and volatile fatty acids (VFA) were measured. Significant interactions (P < 0.01) between ensiling duration and diet were observed for the concentrations of different nutrients and GHG production. SMS levels in diets increased (P < 0.001) dry matter (DM), neutral (NDF), and acid (ADF) detergent fiber concentrations but decreased crude protein (CP) and cellulose levels. Ensiling period decreased (P < 0.001) DM, NDF, acid-detergent lignin (ADL), and hemicellulose concentrations but increased non-structural carbohydrates (P < 0.05). Diets with higher SMS levels had lower (P < 0.001) GP, methane (CH4), and carbon dioxide (CO2) production, together with increased degradability of DM, NDF, ADF, and ADL. Conversely, extending ensiling increased CH4 and CO2 production, degradability of DM, and proportions of acetate and propionate but decreased NDF and ADF degradability. Total VFA and butyrate were highest (P < 0.05) in the diet with 50% SMS inclusion. In conclusion, SMS can replace up to 50% of corn silage in the diets of beef and non-lactating dairy cows; however, extending the ensiling duration is not recommended.