Charlie leaned in to nip the former master on the neck. With a gasp, Rick thought "Oh damn... he's starting to treat me like a beta stud..." To his dismay, he found himself dipping his head to a submissive pose and likeing it.
Charlie rubbed his shaft to Ricks back more and more. "I must admit the one thing I really liked the most aside from feeding and grooming is when you jacked me off. If I hadnt, you'd be flying. You know, that did put you in position of lead mare for me. I always wanted to ride you good and proper. Now I'm the master, and you are in MY herd!"
Rick as horrified at this, but something inside him seemed excited as he unsheathed. He gasped at the size of his mottled pink and brown shaft before Charlie reached down to stroke it. "I see you like your herdmaster..."
Tied, Rick could only watch as Charlie's muzzle dipped to perform the service he had done so many times before. making him squirm and neigh helplessly for several minutes before he came, ..then again...and again, his human seed being flushed from his body with each spurt.
Charlie withdrew when he tasted nothing but horse, licking his square teeth with a wicked grin. "Mmmmm I think you're ready to join the herd, Rick."
With that, he tipped rick across a boulder, and used a saddle strap to tie the tail off to the right. Rick neighed in fear of being ripped in half as the dark shaft probed under his tail. He quickly found to his relief that he had grown larger than his old body, and had the large capacity anus of a horse. It may not be as fatal as he thought, but was still painful... at first.
The shafthead rubbed his prostate, getting him hard again in record time, and the thrusting grew more and more pleasureable.
Being nipped lovingly at the neck made him eager to please his master until they both came together explosively.
Charley nibbled him lovingly as his shaft slipped free. "mmmm, I think it's feed time. I say we go back to camp where you will feed me. I might even change the pack horses."
Rick nodded as he was pulled to his hooves and they started back. His insides were churning, but he wasnt sure if it was his worry at what would happen now, or if it was the load of seed in his butt...