i suggest using flex + it works on my horse and he is 32 and thinks he's still a yearling. also when summer comes around and the flies are getting bad we start all out horses on powdered garlic that we get from a local pizzeria and we use the scoop that comes in the flex + for the garlic and when we use the garlic they only get half of a scoop and we also use fly predators and they works wonders. i have never had any luck with the fly through control it just doesn't seem to work like my past stuff also put a few marigolds in the barn also. all this might sound very crazy but our flies are bad very bad when we don't do this. i hope i was some help i am very sorry if i wasn't