Fermentation Quality, In Vitro Digestibility, and Aerobic Stability of Ensiling Spent Mushroom Substrate with Microbial Additives

SIMPLE SUMMARY: In animal husbandry, spent mushroom substrate has not been effectively utilized as an agricultural byproduct. Ensiling is an important roughage processing method that can not only improve the palatability of feed but also prolong the storage time of high-water feed. At present, due to the different physicochemical properties of various agricultural byproducts, a unified conclusion on the effects of using microbial additives in agricultural byproducts has not been reached. Therefore, this experiment investigated the effects of lactic acid bacteria and cellulase on the fermentation quality, in vitro digestibility, and aerobic stability of Flammulina velutipes spent mushroom substrate silage (F-silage) and Pleurotus eryngii spent mushroom substrate silage (P-silage). It was found that the combination of application of lactic acid bacteria and cellulase is an effective strategy for improving the fermentation quality and aerobic stability of F-silage and P-silage. In addition, cellulase can be used as an additive to improve the in vitro digestibility of P-silage. Our research results provide technical support for a thorough understanding of the effects of microbial additives on spent mushroom substrate silage and provide a theoretical basis for the production of high-quality spent mushroom substrate fermented feed. ABSTRACT: This experiment investigated the effects of lactic acid bacteria and cellulase on the fermentation quality, in vitro digestibility, and aerobic stability of Flammulina velutipes spent mushroom substrate silage (F-silage) and Pleurotus eryngii spent mushroom substrate silage (P-silage). Silage treatments included groups without any additives (control), with lactic acid bacteria (L), with cellulase (E), and with lactic acid bacteria and cellulase (M). Data analysis was performed using independent sample t-test and analysis of variance. After 45 days of ensiling, the pH in F-silage and P-silage from the L, E, and M groups were lower than those in the control group (p < 0.05). The pH, acetic acid (AA), and propionic acid (PA) levels in P-silage were lower than those in F-silage, and the LA content in P-silage was higher than that in F-silage (p < 0.05). Compared with the control, the E treatment increased in vitro neutral detergent fibre digestibility (IVNDFD) and in vitro acid detergent fibre digestibility (IVADFD) in F-silage and P-silage (p < 0.05). The aerobic stability of F-silage inoculated with L increased (p < 0.05) by 24 h compared to the control. The aerobic stability of P-silage inoculated with M increased (p < 0.05) by 6 h compared to the control. The improvement in fermentation quality and aerobic stability is extremely large in terms of applying M in F-silage and P-silage. The E is effective in improving the in vitro digestibility of P-silage. The research results provide a theoretical basis for the production of high-quality spent mushroom substrate fermented feed.