In addition, a monensin byLAD or PO interaction was not observed for the metabolites. Methane production and themethane proportion to total gas production had a diet × monensin interaction (P < 0.01). Themethane proportion was decreased quadratically (P = 0.028) with LAD addition, whereas POaddition linearly increased (P = 0.014) the methane proportion; both of these effects weresmall. Meanwhile, monensin by LAD or PO interactions were not observed for methaneconcentration and proportion. In conclusion, the combinations of monensin and LAD or POin forage and high concentrate diets had no interactions on in vitro fermentation kineticsand end product production.