I've been growing mulberry trees for 12 years for my tortoises. A few years ago I cut one back during the winter while it was dormant and noticed that it produced more leaves and they were bigger than the leaves on the trees that were not pruned. This first pic was taken late April this year. The new growth is just starting to come out. .These pics were taken today.The branch running from bottom right to upper left is one of the first new branches, At the base of each leaf another new limb starts growing This is the size of the leaves on the first new growth limbsNot only will you get more and bigger leaves you wont get any berries on the new growth Also the new limbs stay flexible enough to bend them down to get the leaves that are out of reach. In the fall when the growing season ends I start trimming the limbs back and strip the all the leaves off for food or dry for winter food.