The beef tallow thing… Well the horse owner may have horse dentistry equipment to make it safe… it might work on some horses… it might work the opposite and the horse chows down as fast as he can to clean his mouth.
The reason it might work is that horses are vegetarian and kinda know , “instinct”, not to turn carnivore… But they only have their taste buds to tell them, and they won’t want to be putting their tongue onto the beef tallow. All they can do then is open their mouth and drool, but the beef tallow isn’t coming off is it ?