Same thing happened to me last year and The
trees didn't seem to be harmed. Growth seemed normal. I think if the rabbits chew only through the bark and not through the cambian (the slimey layer underneath) they should be okay. This year I put some
tree tubes with a slit down one side around all my apple trunks. That worked until I took them off to spray my dormant oil and didn't reinstall them. I think a cat is clawing some of my trunks also. Next year I'll get some hardware cloth (wire mesh) and loosely wrap the trunks with it. It should be about 18 inches tall or even higher if you have deep snowfall.
You might want to spray some fungicide on the damaged areas as a preventative, but I'm not sure that's necessary.