Jacob figures there wasn't much point to resisting as the girl moves onto all fours, presenting her pussy to him in anticipation. Jacob can't resist, and mounts the girl, and tries to slide into her, but misses the mark the first couple of tries.
"Nothing to be worried about," the girl says, and reaches back and helps position Jacob's cock by her pussy, and he pushes into her. She moans loudly as Jacob thrusts into her harder, and she smiles as the changes begin to cover her body as she starts to transform into a German Shepard bitch.
"Oooh, that's a good boy, keep going, fuck me and make me your bitch!" She screams out, Jacob needs no more encouragement as he plunges all the way into her tight pussy, his knot locking them into place. As he continues to thrust, he can feel the girl's body changing beneath him, her moans and urgings soon turn into barks as he continues to fuck her.
Jacob was surprised with the way he was acting, dogs shouldn't be having sex with humans, but he no longer cared. By the time he cums inside of her, she's now a full german shepard and the Zoo Lady walks back inside.
"Good boy!" She says, petting Jacob and the girl at the same time. "Now, about that deal we made..."