Mentha piperita (Peppermint) leaves as feed additive: In vitro ruminal gas, methane and carbon dioxide productions, nutrient degradability, and ruminal fermentation kinetics

This study determined how phytochemicals in dried peppermint (Mentha piperita) affect in vitro ruminal gas production (GP), methane (CH4) and carbon dioxide (CO2) production, fermentation parameters, and nutrient degradability of a total mixed ration containing (per kg DM): 500 g concentrate feed mixture, 400 g berseem hay, and 100 g rice straw. Peppermint leaves were included at 0 (control), 0.5, 1.0, 1.5, and 2% of the diet, and the experiment lasted for 48 h. Each treatment was incubated in triplicate bottles across two independent runs, with two blank bottles (inoculum only) per run, to establish a baseline for fermentation GP. Peppermint (p=0.002) decreased the asymptotic CH4 in a dose-dependent manner, and the lag was prolonged with an increasing level of peppermint in the diet. The diet containing 0.5% peppermint had the highest DM degradability, and the diet containing 2% peppermint had the highest neutral detergent fiber (NDF). In comparison, the diet with 1.5% peppermint had the highest acid detergent fiber (ADF) degradation. Diets containing 1.5% peppermint produced the highest (p<0.05) short-chain fatty acids (SCFAs), while 0% peppermint produced the lowest. The addition of peppermint (0.5-2%) improved GP, reduced CH4, and increased the degradability of DM, NDF, and ADF, concentrations of total SCFAs, acetate, and propionate. The best-performing dose that is environmentally friendly and improves digestive parameters is 0.5-1% peppermint in the diet, but further in vivo studies are warranted.