I could be mistaken, but that sure looks like classic deer browse damage to me. Your fencing is inadequate, being too low, too close, and not sturdy enough to prevent future deer damage. So far, no long-term damage has been done. But if not fenced properly, when winter arrives, it won’t be the leaves the deer eat, it will be the buds, which will seriously stunt your tree. I would urge you to make the investment in good fencing to protect your investment in this tree. Good luck!