LAUSR

Abstract The present context was aimed to determine the in vitro gas production (GP), mitigation of methane (CH 4 ) and carbon dioxide (CO 2 ) emission, and ruminal fermentation from nine different tree leaves as suitable alternatives for alfalfa hay. Tree leaves and alfalfa hay were incubated with rumen inoculum from calves at different ages (20, 40, and 60 d). The level of asymptomatic GP [mL/g dry matter (DM)] differed ( P P 4 production (mL/g DM), fractional rate of GP and lag time. The asymptomatic CO 2 production and fractional rate of CO 2 production decreased effectively ( P In vitro rumen CH 4 and CO 2 productions (mL/g incubated DM) by species incubated in the rumen liquor of calves collected at 60 d of age increased effectively. Fermentation pH ( P P  > 0.05) was not significant by dose and substrate × dose interaction. Tree leaves showed lower production of CH 4 (mL/g incubated DM) and proportional CH 4 emission when compared to alfalfa hay after the required period of incubation at significant level ( P P  > 0.05) on CO 2 production (mL/g incubated DM and mL/g degraded DM) and proportional CO 2 production. The incorporation of tested tree leaves in diet would be a valuable alternative of alfalfa hay with sustainable reduction properties of CH 4 and CO 2 productions. These potent tree leaves can be used as valuable cleaner product and feeding stuffs for the environment and ruminants respectively due to their in vitro fermentative properties.