Research into drugs, therapies and nutritional management of equine ulcers is ongoing, and new information is being published monthly. One of the biggest changes to the area of ulcer management is the distinction of Equine Squamous Gastric ulcers (ESGD) that occur in the upper, less protected region of the stomach, and Equine Glandular Gastric ulcers (EGGD), those that occur in the glandular region. By recognizing the types, and causative factors, we can be more accurate in management.
Squamous ulcers occur in the squamous area, that is above the margo plicatus, where there is little to no mucous or protection against stomach acids. Ulcers occur here generally when there is a “splashing” of acid from the lower part of the stomach, which can happen with exercise (when the abdominal muscles constrict on the stomach) or when there is less of a physical barrier between the acidic liquid and the squamous mucosa, both of which can be made worse by an exaggerated acidic environment.
Glandular ulcers occur in the areas of the lower stomach, where glands secrete acids, but where there is normally extensive mucous protection. With these ulcers, both increased acidity and reduced mucous production may contribute to ulcer development.
Gastroscope images of the lining of a healthy equine stomach is shown (left) and severe gastric ulceration in a Thoroughbred racehorse (right). (Center for Equine Health/UC Davis image).
While more research has been focused on squamous ulcers, the incidence of both types is relatively high, with between 11-100% of horses having squamous ulcers, and 3-73% having glandular ulcers. Of course, higher incidence of either type is associated with intense exercise.
Dietary Causes and Buffers
From a nutritional standpoint, dietary management appears to have a greater impact on squamous ulcers. Risk factors of ESGD include reduced forage intake and increased grain/concentrate intake. It is recognized that concentrates, particularly those high in starch, may be fermented to some degree by a small population of microbes in the stomach, producing additional acidic compounds (volatile fatty acids, including acetate and lactate). These acids, plus the continuously secreting hydrochloric acid from parietal cells in the glandular region, create a highly acidic environment. Therefore, feeding diets with more calories coming from fibre and fat may be favorable over traditionally high starch feeds.
Equine Stomach. (Source: Advanced Strategies of Drug Delivery via Oral, Topical, and Parenteral Administration Routes: Where Do Equine Medications Stand?)
It should be noted that some other feeds may also be high in starches and sugars, in particular pasture. That said, forage intake may contribute towards preventing against gastric ulcers in two ways. First, the extra chewing required to break down forages prior to being swallowed produces saliva, which is high in bicarbonate, a natural antacid. Secondly, the longer particles of forages that are swallowed tend to “float” on top of the acidic liquid based on gravity, and thereby produces a physical barrier so that acid can’t splash as much.
If alfalfa is the forage of choice, there is the added benefit of extra calcium that can also buffer acid. New research has suggested that marine-based calcium are even more efficient antacids.
Offering some of these feeds, and/or offering some alfalfa regularly, and perhaps prior to exercise, may help neutralize the acids and reduce the splashing to that squamous area. There are several nutritional supplements, including plants and extracts (sea buckthorn and aloe), protective agents (pectins and lecithins) and mineral buffers (primarily calcium and magnesium) that may show some efficacy to help minimize acidity and protect the squamous area.
Of additional interest were some findings that the provision of hypertonic electrolyte solutions increased the severity of squamous ulcers. Another study reported an increased risk of ulcers in obese horses. While there is also significantly less research focusing on nutritional risk factors associated with EGGD, there also appears to be less of a nutritional influence. This is likely due to the fact that it is believed that EGGD is caused more by inflammation or infection, and thus contributing to reduced mucous production and protection.
Management
Medical management of ulcers is more successful with squamous ulcers, in part because the causative factors are better understood – decreasing acid can improve squamous ulcers. Acid suppression, along with mucous production stimulation, may help with EGGD. Your veterinary professional will have the most up to date advice on medical management.
Acid production can be reduced through the actions of a class of drugs called proton pump inhibitors (PPIs). Within the parietal cell of the glandular region, hydrogen is pumped into the stomach lumen along with chloride (hydrogen chloride). PPIs inhibit the H+/K+ ATPase pump, thereby directly decreasing acid secretion into the stomach.
There are several types of PPIs available for horses, with Omeprazole (Gastroguard, Ulcerguard) and Esomeprazole (Nexium) being the most common. Omeprazole is the most common treatment used for horses, although there are differences in its effectiveness based on dose, duration and absorption. In general, a dose of 1 mg/kg BW is most effective when administered prior to feeding in about 75% of horses. There are also intravenous forms of omeprazole; however, it needs to be injected daily. An intramuscular form is also promising as it appeared to be more effective than oral omeprazole over a treatment time of four weeks.
Esomeprazole has been shown to be effective in some cases when treatment with omeprazole failed. A dose of 2 mg/kg BW has been shown to elevate stomach pH in horses fed hay. At doses of 4 mg/kg BW, esomeprazole appeared to be more effective than a Gastroguard alternative treatment of omeprazole. It should be noted that omeprazole, and likely esomeprazole, can result in rebound acid hypersecretion, which can make reoccurrence of gastric ulcers likely.
Omeprazole is approved for use in horses in the US and Canada, while esomeprazole is available as the common (and less expensive) human heartburn relief drug Nexium, but is not currently approved for horses by the FDA.
Another class of drug for gastric ulcers are H2-Antagonists/Blockers. These drugs block histamine from stimulating the H+/K+ ATPase pump, thereby indirectly decreasing acid secretion into the stomach. These drugs may be considered to compliment PPIs, but appear to be less effective. Drugs in these classes include cimetidine (Tagamet) and famotidine (Pepcid), as well as ranitidine (Zantac). Ranitidine is no longer on the market due to its cancer-causing effects.
Sucrulfate is a polyammonium hydroxide salt that helps protect the glandular mucosa. It may be offered 30 minutes after omeprazole prior to feeding. Misopristol is another drug that is believed to improve bicarbonate and mucous secretion, and while it may show promise and warrants further research, it can be dangerous to humans handling it, causing miscarriages, premature labour, or birth defects when handled by pregnant women.
An important part of the management and treatment of any type of ulcer is the correct diagnosis. While clinical signs can be indicative, gastroscopy is the best way to confirm ESGD, and is also highly useful for diagnosing EGGD. Clinical signs such as colic, poor performance and weight loss may indicate gastric disease, and should be discussed with your veterinarian.
It is important to discuss any digestive concerns with your vet and take appropriate measures. However, it is also important to discuss your feeding regimen with your nutritionist, particularly if there are digestive issues. Nutritional management may be a vital component of your ulcer management plan, and could be key in helping you prevent them in the first place.