My horseshoe guy suggested giving approx. 1 oz. per 1,000 lbs weight apple cider vinegar to my mare daily as an aid in her regular worming schedule, and said it would also help with eliminating sand from her gut. I've heard of feeding garlic to repel flies, but how much? Also has anyone ever heard of feeding vinegar as helping in repelling flies? I'm trying the vinegar this season starting before theflies really get started. My Sugarpop gets 1 oz. every evening diluted with a little Grand Hoof, some alfalfa flakes, and a little pancake syrup for flavor. Are there any others who've given vinegar for any reason?