Mike could not hold back any longer - or more accurately, the stallion could not wait. Instincts and desire overwhelmed Mike's conscious thoughts and he slid up over the mare's back in a practiced, fluid motion. This time he found her opening the first time, and plunged deep with the first thrust. She clamped around him, and he rocked back and forth, his member throbbing and almost aching. His teeth found the back of her neck and she whinnied as he bit her. The intense orgasm was joined by a flare of the transformational magic that rolled up from his loins and seemed to explode through his upper chest and head. He rocked and thrust and felt himself empty into the mare, his screaming neigh matched by one from the mare. Once, twice more he shuddered, and then he was empty and the mare was full.
Panting, his massive equine chest heaving and dropping with sweat, Mike slid off the mare and stood next to her, rubbing his chin over her back. It took a few minutes for thoughts to clear enough to realize he had a full equine head. A full equine everything. Twisting around, he saw he had completely transformed into a Shire stallion. Larger then the female, healthy, mature. He remembered being human, then being a centaur. But Mike was a horse now. He struggled a little with comprehension - very smart for a horse - and there were memories of his past, even if they were getting harder to make sense of. There was no point in regret or worry. Mike the Shire snorted and relaxed, accepting his new lot in life.