Tie hay nets securely and high enough so your horse can not get his leg caught in the net. Keeping your horse and his living quarters clean will minimize parasite reinfestation, cut down on grooming time, and help him look great. This includes cleaning up manure, keeping the area around the barn and pens dry and keeping flies and other pests to a minimum. Horses that stand in wet manure and urine have a higher incidence of thrush and other hoof problems. Remove wet bedding from stalls daily and allow stall floors to dry before rebedding.
Stable flies bite a horse's skin until it bleeds and then feed on the blood.
Favorite sites are lower legs, flanks, belly, under the jaw, and at the junction of the neck and the chest. Stable flies lay their eggs in manure, wet hay, unclipped grassy areas, and other places where there is moist plant material. Repair leaking faucets, hoses, and waterers. Keep stalls and pens dry. Clear away wet bedding, sprinkle lime or a stall deodorizer on the wet spot, and let the ground dry before adding new bedding.