I hope Prince finds many Yorkie friends and has the chance to build his muscles stong and healthy.
Swimming is an excellent idea to aid in his therapy. I have done this with Schatzie, we have a garden tub and we both just climb in there together and I hold her tummy while she exersizes. (Have lots of towels on hand, you will need them, LOL)
If Schatzie lived closer she'd love to play with Prince.
