a method of treating adverse behavior in animals , manifested in secondary effects such as , in horses , excitability , difficult handling , coprophagy , wood chewing and grasping , or wind sucking , by controlling the formation and accumulation of acid in the hind gut of the gastrointestinal tract that results from the fermentation of excess carbohydrates in the hind gut . this is accomplished by ingesting certain antibiotics with or without combination thereof with certain enzymes . of specific merit in this invention is the use of virginiamycin to control the passage of carbohydrates into the gastrointestinal tract and the fermentation of these carbohydrates therein . this controls , the accumulation of acid in the digestive tract .