Dr Grow (Patreon)

She used to be the owner and only doctor at a veterinary clinic, specializing in care for livestock. But, after accidentally sticking herself with a needle intended for strengthening a horse with a new product, she found her body putting on muscle at a clothes-splitting rate, until she was sure she was as strong as a whole team of horses. She also later found out that, had she stuck the horse instead of herself, it would have been five times the recommended dosage, and would have turned the sleek and lithe Arabian into a horse stronger than all but the strongest of Clydesdales (big, muscular draft horse for pulling heavy loads).

I pulled this one out of my collection of scenes from before I started posting to DA and Patreon. A few tweaks, such as applying new morphs that I got or made since putting this scene together, and then throwing in a backdrop and setting up cameras, and then this was ready to go.