Hacking horses may have ulcers because of large irregular concentrate meals. When a horse's stomach remains empty for hours, (this is not as common in horses which have adequate grazing all day) then filled for a short period, the stomach acid and pepsin have access to unprotected stomach lining and can gradually form a hole in it. The protective mucus layer in the stomach is thinner in some places and excess acid can damage the walls, contributing in ulcers.
Stomach ulcers could be responsible for your horses' bad behavior. Here is something I found particularly interesting; your horse may alter his gait to decrease discomfort, as well as exhibit general bad temper, restlessness, and poor performance. Recurring hind end lameness avoids movements such as changing canter leads. A dull rough coat or color change, chronic colic, limited appetite, back or neck pain, difficulty maintaining weight, and decrease of muscle tone despite exercise can all be signs of ulcers. Vertebras can be displaced by a horse trying to stop painful movement. Some horses never show signs of ulcer irritation; this does not mean they are not present! To be sure, have an endoscope carried out on your horse to diagnose this. Foals are also susceptible to ulcers. Foals might have drooling saliva, reoccurring colic, diarrhea, they may grind their teeth, or show inconsistent nursing, they could even lie on their backs with their legs in the air to relieve the pain.
Herbs such as comfrey, marshmallow root or licorice, also assist with gastric ulcers. The high mucilaginous content in the comfrey leaf helps to heal and soothe the stomach lining. Marshmallow soothes the entire digestive tract and licorice helps reduce stomach acid by producing mucus that acts as an anti-inflammatory. To decrease stomach acidity and reduce inflammation, try aloe vera gel orally (2 oz added to the feed regularly), it works as an anti inflammatory and also cools off the system but reducing heat in the intestines during fever. For bleeders, use the gel in a nebuliser. Relief from ulcers may bring much needed comfort to both you and your horse!