Based on in vitro results, common ash (Fraxinus excelsior) and white mulberry (Mores alba) could serve as a useful form of alternative forage during the dry part of the summer, when grass resources are lacking. To better understand the forage potential of these two species, we formed two experimental groups of six adult sheep in their maintenance phase. Each group was offered leaves from one species ad libitum. A third group of six sheep was fed hay from a permanent grassland. For three weeks, we measured forage intake and digestibility. We found that the sheep consumed large quantities of the leaves, which were well digested. Thanks to their low fibre content, the leaves could be fed to animals with high resource needs, whether during the growth stage or the production stage. Future research should examine the forage potential of additional tree species found in temperate zones.