Hello, recently I have noticed flies have been biting at my horse, liam's, sheath and its beginning to swell. I have tried everything, swat (melted off), copious amounts of flyspray, flysheet, fly predators, etc. I also muck the paddock they live in daily and their stalls when dirty. I don't know what else to do to help him, I don't want it to develop into a summer sore or anything worse. If there are any tips to help keep the flies off the sheath area please let me know! also heard apple cider vinegar in their feed could help but i'm not sure if there is science backing that or not. Another thing I should add is my other gelding is not being bothered to the extent as liam is. Thanks in advance!