Fermentation parameters and methane emissions of basil-based diets evaluated using the in vitro gas production...

This study aimed to investigate the effects of incorporating basil (Ocimum basilicum) as a partial replacement for alfalfa and wheat straw on in vitro ruminal fermentation, methane production, and nutrient utilization. The experiment evaluated three dietary treatments: a control diet (0% basil) and two basil inclusion levels (12.5% and 25%) substituting alfalfa and wheat straw. Chemical analysis revealed basil had a moderate crude protein (6.65%) and high neutral detergent fiber (54.26%) content compared to alfalfa and wheat straw. In vitro gas production assays demonstrated that the inclusion of basil at 12.5% and 25% levels significantly reduced (P < 0.05) cumulative gas production volumes across all incubation times from 8 h onwards, compared to the control. Potential gas production (b value) and metabolizable energy content declined linearly (P < 0.0001) with increasing basil levels, indicating lower fermentable organic matter in the basil plant. In vitro organic matter digestibility and short-chain fatty acid production were also maximized for the control diet. Notably, methane production decreased substantially (P < 0.0001) as basil forage inclusion increased, from 7.65 mL/200 mg DM for control to 7.09 and 4.53 mL/200 mg DM at 12.5% and 25% basil levels, respectively. Moreover, the reduction in ammonia nitrogen concentration (P = 0.0003) with increasing basil levels suggests improved nitrogen utilization, which could lower nitrogen excretion and its associated environmental impacts. Ruminal fluid pH remained stable across treatments, maintaining optimal conditions for microbial activity. In conclusion, the basil plant shows significant promise as a methane-reducing feed additive, contributing to environmental sustainability by lowering greenhouse gas emissions and enhancing nitrogen efficiency.