Evaluation of Lactobacillus plantarum MTD1 and waste molasses as fermentation modifier to increase silage quality and reduce ruminal greenhouse gas emissions of rice straw.

Lactobacillus plantarum and molasses have been shown to function as fermentation modifiers in both silage and rumen fermentation. This study aimed to evaluate the effects of L. plantarum MTD1, a commercial probiotic, when co-administered with waste molasses (WM), on the silage quality, rumen volatile fatty acids and greenhouse gas (GHG) production of rice straw. Rice straw was ensiled with no additive (Control), 106 cfu/g L. plantarum (L), L + 2%WM, L + 3%WM and L + 4%WM for 3, 6, 9, 15, 30 and 60 days. The rumen volatile fatty acids and gas production kinetics were determined using in vitro incubation technology. All additives, especially L + 4%WM, improved the silage quality of rice straw, indicated by higher lactic acid and nonstructural carbohydrate content, lower pH, butyric acid and ammonia nitrogen content (P < 0.05). A simple linear regression showed that the ruminal propionic concentration increased (linear, P < 0.0001) and the ratio of acetic to propionic acid decreased (linear, P = 0.0002) as a function of WM dose. The 60-day ensilage could decrease ruminal total gas production by 13.51-31.29% as compared to the untreated rice straw. Wherein L had no effect on the mitigation of CH4 but decreased the CO2 production, and further WM inclusion decreased the CH4 production with a dose effect. If the better silage quality and lower ruminal GHG production observed in the study are confirmed in practice, applying L + 4%WM may provide an insight for straw waste management while reducing pollution input into the atmosphere system. This in vitro study can be valuable for screening and informing on the suitability of these fermentation modifiers for further evaluation in vivo.