Jacob braced himself as he felt the hard prod, then got shoved forward as the bull tried to enter him. The thick shaft was just too big. He tried to help by pressing back as the bull, wishing there was a way he could feel the massive cock. As that thought crossed his mind, he felt a strange throbbing that started in his butt and rolled all the way out to his fingers and toes. The bull shifted and turned away, apparently no longer interested in trying the offered opening. But when he moved, Jacob was dragged with him! Bewildered, he tried to pull free but was stuck fast to the end of the bullcock. Even stranger, his legs were getting weaker. Twisting around as best he could, Jacob looked back and gasped. His legs were shrinking away! At the same time, the bull's ballsack was inflating, now carrying what looked like melons. The bull stopped and bellowed, and Jacob was lifted up from the ground as the animal erection stiffened again. He struggled frantically, flailing his arms as his back arched to match the thick shaft he was now part of. A scream was cut off as he threw up suddenly, but what came out of his mouth was thick, off-white semen. The bull bellowed and started thrusting as he stood there, causing Jacob to swing wildly. He spewed more bull cum each time, and had to struggle for breath. When the bull finally seemed to have finished, Jacob realized that his arms were little more than nubs, and his body had shrunk down and turned black. He was no longer breathing, and a steady pulse of blood was filling him from the bull's heart. He was becoming the bull's cock! The animal bellowed again and he felt himself stiffen. This time, a powerful sensation of pleasure overwhelmed him as more semen shot from his mouth, and other senses shut down as his eyes, nose, and ears vanished into what was now the end of a bull's penis. But Jacob was still aware - he remembered who he was, and could feel the pleasure, and taste the cum as it shot from the piss-slit that had been his mouth. The pressure filling him slowly eased, and he sank back into the dark cave of the bull's sheath. Still fully aware, Jacob was now the bull's cock. What would happen when the bull mounted a cow? Jacob was afraid that he might end up fading away, but at the same time, he was fascinated by the new sensations of being the animal's cock.