Ever since I was a kid I've been into the concepts of body swapping and TG transformations, but lately I've come across some stories/art where a guy transforms into a cow girl and that's become one of my favorite kinds of MTF transformations.
My personal story for it though is a much less NSFW one A guy works at a farm, accidentally gets caught up in a high tech machine, gets injected with a serum that first transforms him into a woman, then the cow like stuff comes in (A tail, horns, cow ears, bigger breasts that start leaking milk), the machine is actually a milking machine and the milking process starts, the guy/cow girl feels incredible sensations and starts letting out a few moos but is trying to fight it off, call for help, and escape but eventually gives into the pleasures and lets the process continue.
During the milking now, the now hucow seems to have lost her intelligence and can only moo now, but that's not exactly the case. After being found by the owners hours later, she's placed in a more secure part of the farm. Her intelligence and ability to speak return not too long after the milking and she's scared, confused, and embarrassed. She vows to escape and find a way to turn back to normal, but it will be a challenge. Thankfully she isn't alone. There's another hucow at this farm. A formally more simple minded woman who embraced her transformation and new life befriends the former man/current cow girl.