You can't help but feel sorry for cattle and horses, plagued as they are by flies. There isn't a lot you can do about it, though. Spray works for a few hours, then the flies are back. You can buy insecticide ear tags for cattle that last about six weeks, to control face flies. I think we may try those next year. Of course that means getting the cattle confined and forcing each one, in turn, to put her head in a headgate that holds them still. Which can be quite a rodeo.
These girls are twins, but I recently noticed the one facing left outweighs her sister by at least fifty pounds. Maybe now I could name them, since I have a way to tell them apart.