... you don't notice she isn't having to lift her head quite as high to reach your crotch. Your doggie shaft is fully engorged again, and the fur-covered balls that you thought you just emptied are churning.
She stops and sniffs you, then barks and rubs against you before turning and presenting her rump to you. It is hard to think of anything but the bitch's dark cunt, and the throbbing pink shaft between your furry legs. Part of your mind realizes that your legs weren't furry before, and that they also look a lot different. In fact, your Sheepdog dick and balls look right at home between Sheepdog hind legs.
You are shaking, almost unable to resist the female's scent and your own horniness. But if you mount her and satisfy yourself, you might finish up as her mate!