A good lab can do a lot of work.
That said, I would send my neighbors dog after a beaver unless I was 100% sure it was dead. A beaver can flat fugk up a dog, especially in the water.
Without any doubt...a Beaver with some life left is a different fight than a wing tipped Goose on the ground.
I’ve seen a Groundhog mess up a Dog-although I had one that killed them rather easily-and a Raccoon take the fight out of one rather quickly. I have little doubt I wouldn’t want my Dog latched onto a Beaver that decided to go home..