Exploring the In Vitro Effects of Cassava Diets and Enterococcus Strains on Rumen Fermentation, Gas Production, and Cyanide Concentrations

This study examined the effects of adding CUB alongside HCN sources from fresh cassava diets on HCN reduction, gas production, and in vitro digestibility. A completely randomized design (CRD) with a 2 × 2 × 3 + 1 factorial approach was used, where Factor A was the HCN source [fresh cassava root (FCR) or leaf (FCL)], Factor B was the HCN concentration (300 and 600 mg/kg dry matter (DM)), and Factor C was the bacterial supplement [no-CUB, <i>E. faecium</i> KKU-BF7 (CUB1), and <i>E. gallinarum</i> KKU-BC15 (CUB2)]. Statistical analysis was performed using the PROC GLM procedure in SAS. No interaction was observed among the main factors on gas kinetics and cumulative gas (<i>p</i> > 0.05). The addition of CUB1 or CUB2 enhanced cumulative gas production compared to the no-CUB group (<i>p</i> = 0.04). Cyanide degradation efficiency was high when FCR was included at a high HCN level. At 12 h post-incubation, HCN degradation efficiency was higher in the CUB2 and CUB1 groups, reaching 98.44-99.07% compared to the no-CUB group. The higher HCN level increased in vitro acid detergent fiber digestibility (IVADFD) (<i>p</i> = 0.01) by 7.20% compared to the low HCN level, and CUB2 further improved IVADFD. Compared to the FCL-fed group, FCR supplementation increased total VFA concentration (<i>p</i> = 0.03) and propionic acid (C3) concentration (<i>p</i> = 0.04). The addition of CUB2 further enhanced propionic acid concentration by 8.97% compared to no-CUB supplementation (<i>p</i> = 0.04). These results indicate that supplementing <i>E. gallinarum</i> KKU-BC15 at the highest HCN levels in FCR boosts HCN degradation efficiency, fiber digestibility, total VFA, and C3 concentration.