The likely culprit for the bark damage is rabbits.  Deer are also possible, but they tend to chew further up the tree, and you had a cage around the trunk.  The damage has been done, but it's possible the trees may survive.  It doesn't look as if the bark has been girdled- chewed all the way around.  You can wrap your trees or put a plastic protective cover around the trunk to prevent further damage, but only time will tell if they have been damaged to the extent that they will not survive.  For information on growing apples in the home garden, including a section on protecting the. trees from wildlife, see https://extension.umn.edu/fruit/growing-apples