Also, sorry for the double reply, but maybe you could check out SlutCraft. Not sure if the game is completely finished yet, but you get a few hours of gameplay in there. It's more captivity than slavery, though. Same thing with Earn Your Freedom, although if you're not into traps, I suggest you stray far from that game. Tales of Androgyny has a mini-game related to being a breeding slave for centaurs after you get a game-over being defeated by centaurs 3 times, but as the game's title suggests, if you don't like hermaphrodites/futas, traps, you should also stay away from this game too.