There is already a cock version for the horse but no mare gens, only for centaur and I dont like to spend weeks to make it for the horse (I'm a neko) we dont have time XDNot saying it so you would do it if it's not your thing, but you actually have horse assets as well as genitalia assets for them (and dogs as well). Granted, the genitalia doesn't "fit" the horse model, but you can parent and use it