Horse sick with cold/flu, not eating anything?

He isn't eating anything, but we haven't tried apples or carrots or treats like that. Do you think like a bran mash might work? I have heard of making those, but I have never tried making one myself. If you suggest that, what do you use and how do you make it? Is there any feed that I can buy here in Saskatchewan that will help him actually eat and soothe whatever is wrong with him? We board our horse, and like three months earlier a horse died from something, we don't know what, but he didn't eat anything either. There are other horses there that are sick, so I've heard, and the person that owns this place refuses to go to the vet with these horses because it costs too much and then we'd have nobody to trailer the horses. She has taken some clinics with vet work, and she has all of this medication. We have no idea how this was caused, how to cure it, or when it happened.