Update on Ulcers
- Sep 30, 2008
Ulcers In Three Days
Recent studies have shown that within just three days of a stress condition, a horse can develop gastric ulcers. Frank Andrews, DVM, MS, Dipl. ACVIM, formerly of the University of Tennessee and now the director of the Equine Health Studies Program at Louisiana State University's School of Veterinary Medicine, has been at the forefront of gastric ulcer research.
"For gastric ulcers to develop there needs to be exposure to hydrochloric acid (digestive juices of the stomach) and to volatile fatty acids (VFAs) and organic and bile acids," says Andrews. (VFAs are fermentation byproducts of sugar sources found in hay or grain, while bile acids reflux from the small intestine.)
"With just three to four hours of exposure to these substances, tissue resistance dramatically decreases. If acid exposure continues, tissue begins to slough away, with severe damage within 12 hours."
Scott McClure, DVM, PhD, Dipl. ACVS, assistant professor in the Department of Veterinary Clinical Sciences at Iowa State University, examined the impact of stress conditions on development of ulcers. His study reproduced conditions involved with attending a horse show-- the horses were hauled for four hours, stabled in a box stall for three days, exercised on a longe line twice daily, then transported home.
The horse’s stomach, as seen by endoscopy, showing extensive lesions with deep ulceration and bleeding in the stomach lining.
"On Day 5 we could already see reddening and thickening of the stomach lining," says McClure. "Seven of 10 horses had some ulcers, although not large ones. If you maintained the stress, you would likely see some early clinical signs, like decreased feed intake and general ‘uncomfortableness' of the affected horses."
McClure notes that changes to the stomach lining are visible via endoscopic exam by Days 5 or 6, whereas clinical signs don't generally appear until Days 7-10. Small ulcers that are visible at Day 5 show significant ulceration by Day 8.
Ulcers in "Low-Risk" Horses
McClure has been struck by the number of recreational or low-performance equine athletes with some degree of gastric ulceration. He says, "In previous GUS studies, about half of clinically normal yearlings and mature horses were affected. We are now finding that about one-third of lesson horses have ulcers, and most of these are calm horses in a stable living situation."
He continues, "The lowest incidence of ulcers that I've seen is around 10%. While there is some level of ulcers present in a ‘normal' population, the more people do with their horses, the higher the incidence climbs. I suspect that by midsummer, ‘weekend' horses have a 50% incidence of GUS. Younger horses and high-strung horses are likely to be more at risk, while an older, seasoned traveler may be less likely to develop GUS."
Along Those Lines
McClure has seen horses that "live on the road, yet don't have ulcer problems. That is the environment they are used to, and they have the benefit of filled hay bags hung in front of them almost all of the time."
Looking at environmental factors, McClure stresses that change is the major factor: "It seems that problems develop when horses are stalled in new barns, when started into showing or training, and when being hauled, especially early on in their careers."
Research by Sarah le Jeune, DVM, Dipl. ACVS, ECVS, CVA, at the University of California, Davis, School of Veterinary Medicine yielded some interesting revelations about gastric ulcers in broodmares. The population of 62 mares in her study were managed similarly and maintained in irrigated grass pastures.
Nonpregnant mares were fed straight alfalfa, while pregnant mares received a mix of 50% alfalfa and 50% grass hay twice daily. All mares were fed two pounds of grain once daily.
She says she was surprised that the "overall prevalence of gastric ulcers was about 71%."
While ulcers were mild, she says, "These findings should increase the awareness for gastric ulcers in a population of horses that was previously thought to be at a very low risk of developing this condition."
Feed and Feeding
The mechanical breakdown and mixing of feed in the stomach reduces large meals to smaller particle sizes so feed can pass into the small intestine. Andrews says the equine stomach takes approximately 12 to 14 hours to completely empty solid material (hay/grain). However, in a recent nuclear scintigraphy study a pound of grain, when fed alone on an empty stomach, took just 4½ hours to empty from the stomach. This shows that grain empties rapidly from the stomach leaving behind just acid, which can irritate the stomach and cause ulcers. Hay and grain fed together will buffer stomach contents and decrease acidity.
Feed materials, in particular, grain, end up near the margo plicatus, the conspicuous folded edge of the mucous membrane between the nonglandular and glandular portion of the stomach, where the stomach lining is in almost constant contact with its contents. The feed sits as it is digested; bacteria and resident Lactobacillus microbes prefer an acid pH around 4½ to 5 for fermentation. The result is production of VFAs (volatile fatty acids) and other acids.
"A general rule for feeding grain (corn, oats, barley, or sweet feeds) is to limit grain to less than 5 pounds at any single feeding of a 1,000-pound horse, or one-half pound per 100 pounds body weight," says Andrews. "The interval between grain feedings should be at least five to six hours to prevent reaching a threshold whereby VFAs and acid pH could increase the risk of ulcer development."
Bicarbonate, which acts as a buffering agent, is released into the saliva with chewing. Forage, especially alfalfa, in a full stomach also serves as a buffer. Andrews adds, "Alfalfa hay ‘protects' the stomach by buffering stomach acid and increasing the pH of the gastric juices, with one flake of alfalfa hay buffering stomach pH for five to six hours. This effect may not last as long with alfalfa-based pellets or cubes because the small size of the pellets might hasten stomach emptying."
Could electrolytes cause ulcers? Research (Holbrook et al., 2005) showed endurance horses given electrolytes have a higher incidence of ulcers—67% in endurance horses compared to 58% in show horses. Holbrook reports, "Electrolyte administration, dose, and frequency in this study mimicked common replacement strategies used in distance competition during high heat and humidity conditions. Such electrolyte supplementation may induce gastric ulceration or worsen preexisting gastric ulcers."
Gastric ulcers are not alone in causing health problems for horses; colonic ulcers also play a role. Joe Pagan, PhD, president and founder of Kentucky Equine Research (KER), promotes the use of a high-fiber diet to promote colon health. He believes buffering the equine hindgut could counteract adverse effects from rapidly fermentable pasture fructans and/or grain.
Pagan's research team has formulated a time-released buffer product (EquiShure) that remains intact during passage through the stomach and small intestine to reach the hindgut in a usable form. There it can attenuate the decline in fecal pH and limit lactate (the ionized form of lactic acid, which acidifies the colon). Less acid in the hindgut should help prevent ulcers.
Pagan is optimistic, saying, "We have received reports from racehorse trainers that EquiShure supplementation has improved appetite in racehorses fed high grain intakes, which suggests it may have a favorable effect on the lining of the hindgut."
Still, Pagan cautions: "Feeding a buffering agent is certainly no substitute for managing a horse's feeding program to minimize hindgut acidosis (abnormally high acidity in the large intestine/colon)."
New Methods for Ulcer Identification
Until recently, the main diagnostic tool used to establish an accurate diagnosis of gastric ulcers was a 3-meter long endoscope inserted through the nose and down into a horse's fasted stomach. This method only allows visualization of the stomach (the veterinarian can't see the colon).
Now there is a stall-side test that measures occult blood (not visibly apparent) in a horse's feces, and it can differentiate between blood derived from the stomach or the colon. Andrews believes the new fecal blood test (Succeed Equine Fecal Blood Test by Freedom Health) might have merit for ulcer diagnosis since it is 70-80% accurate in identifying a horse with a bleeding intestinal ulcer based on blood components passed into the feces.
The test uses two strips--one to identify equine-specific albumin and hemoglobin. When a stomach bleeds, both albumin and hemoglobin are released, but albumin is digested and absorbed in the small intestine, with only hemoglobin moving on into the large colon. However, a horse with a bleeding colonic ulcer will pass both albumin and hemoglobin into the feces. Recent studies have linked poor performance to anemia created by low-grade bleeding of ulcers.
Even though the test is convenient, it isn't foolproof. Andrews says, "If you get a positive fecal blood test, you know there is a problem, but if the fecal blood test comes up negative, you still don't know if ulcers are present because not all ulcers may produce enough blood to test positive."
Another screening technology, called the SmartPill, has potential value in detecting delayed gastric emptying time that might be associated with ulcer disease. The SmartPill is ingested and collects data as it travels through the horse's intestinal tract.
Andrews explains, "The SmartPill GI (gastrointestinal) Monitoring System measures gastrointestinal pH, pressure, and temperature. In a study in dogs and one horse, we measured gastric emptying time, small and large bowel transit time, and total transit time. Although we don't know how gastric ulcers affect the last two figures, chronic pyloric or duodenal ulcers (those of the stomach and proximal portion of small intestine) could delay gastric emptying and, thus, delay emptying of the SmartPill from the stomach."
Safeguarding the Stomach
Some medical strategies have focused on protection of a horse's stomach against ulcer development, including supplementing the diet with fat or oil. However, Andrews reports, "There is conflicting information on the use of oil for managing GUS. Comparison of rice bran oil and corn oil showed no differences for treatment and prevention of nonglandular ulcers. But, another study found that 8 ounces (1 cup) of corn oil given twice a day with some grain decreased total acid production in the stomach and increased protective prostaglandin E (an inflammatory mediator that plays a protective role in the GI tract). Corn oil might help protect against glandular mucosal ulcers related to NSAID (non- steroidal anti-inflammatory drug) use, but may not have an effect on the nonglandular mucosa, which is where the bulk of stomach ulcers develop in the horse."
In people, bacterial infection is a primary cause of glandular ulcer disease, but it likely has little impact on the nonglandular disease that horses experience. Although Helicobacter DNA (the bacterium that causes human ulcers) has been identified in equine stomachs via positive PCR tests, no published work has yet isolated this organism in equine gastric ulcers."
Still, in ulcer cases that don't respond to treatment, the ulcer bed is often found to be colonized by stomach bacteria. Andrews explains, "Rats with ulcers were drenched with E. coli bacteria and compared to a control group that received a placebo--ulcers in rats given E. coli took longer to heal. Then, Lactobacillus (resident stomach bacteria) was given to half of the E. coli-drenched rats, and the other half received a placebo. Those given Lactobacillus experienced healing. It is speculated that the Lactobacillus may compete with E. coli in the ulcer bed, allowing the mucosa to heal."
The conclusion is that horses with gastric ulcers might benefit from supplementation with probiotic fermentation products, which could contain different organisms than those that naturally occur in the GI tract. Andrews urges owners to discuss probiotic products with their veterinarians; these products are not regulated and there might be quality control issues.
Neigh-Lox, a calcium carbonate antacid, might have some protective effects when supplemented to at-risk horses, says Andrews. Because it only buffers the stomach pH for two hours, it might need to be fed as often as four to six times per day.
Andrews says researchers have studied seabuckthorn berry extract (SeaBuck Complete), which comes from the Tibetan mountains. This extract has been used to prevent glandular ulcers in people and rats. When researchers administered 3 ounces of this liquid extract daily to horses, there was a decrease in number and severity of glandular ulcers, with overall lower ulcer scores.
Andrews remarks, "While there is no statistical difference in using this product, ulcers in seven out of eight horses in a feed-deprivation period stayed the same or improved when supplemented with seabuckthorn berry extract."
Effective pharmaceuticals for ulcer treatment are available, and a new NSAID is reported to be less damaging to the stomach lining. Cyclooxygenase (COX) inhibitors are targeted medications; COX is an enzyme that generates inflammatory mediators called prostaglandins. Certain prostaglandins are helpful and others are not. Many NSAIDs inhibit the COX pathway, blocking production of all prostaglandins. Firocoxib (Equioxx) inhibits the "bad" COX-1 prostaglandins while sparing the "good" COX-2 prostaglandins, such as those that produce mucus to coat the stomach.
"Data from firocoxib (Equioxx) reported that horses in the clinical trials had no ulcer lesions on necropsy," says Andrews.
He says this medication requires a loading dose of two to three times the recommended daily dose, and there is a lag time for Equioxx to exert its anti-inflammatory effects. In light of this, he says, "This medication is a useful replacement for other NSAIDs (phenylbutazone, Bute, or flunixin meglumine, Banamine) for chronic arthritis, but is not useful for an acute condition such as colic or laminitis."
Andrews believes omeprazole (Gastro-Gard/UlcerGard) has stayed true to its claims as a treatment and preventive EGUS medication. On occasion, he has seen horses that have not responded to 60 days of omeprazole therapy, and despite improvements in the pH of gastric secretions, their ulcers sill persist, possibly due to bacterial colonization of the ulcer beds.
Andrews has been evaluating the use of intravenous (IV) omeprazole for hospitalized horses that cannot take the oral form. Intravenous use applies to horses with gastric reflux, colic cases both pre- and postoperative, dysphagic horses (those that have difficulty swallowing) such as ones with botulism, other surgical conditions that preclude oral intake, and horses with imminent rupture of a gastric ulcer.
"For a sick foal," he says, "intravenous omeprazole is used prophylactically if a foal is still well enough to get up and down. Use of omeprazole in recumbent foals may be a problem--such a foal does not typically have much acid in the stomach and clostridial organisms tend to proliferate in a more basic pH in the stomach environment, potentially leading to enteritis (inflammation of the small intestine). A neonate that can rise will have a high acid production and so (will) benefit from IV omeprazole treatment."
Andrews recommends using UlcerGard (which has a lower dose of omeprazole for EGUS prevention) through the show season in horses with chronically recurring ulcers. He says, "If this is cost -prohibitive, then a horse can be started on GastroGard 48 hours before a show, then for 48 hours following the competition. It is necessary to report it on the medication form."
Both products require three to five days to reach a steady level in the body; after the first dose, there is only 25% inhibition of the parietal cells (large oval cells of the gastric mucous membrane) that secrete gastric acid. Withwith that in mind, Andrews says to start omeprazole at least two to three days prior to stressful situations. Alternatively, you can use an H2 blocker, such as ranitidine, which inhibits parietal cells with the first dose, but this medication must be given three times per day for continued effect.
Andrews cautions, "You can't always tell if a horse is stressed. Often the horse that is anxious and nervous with stall vices doesn't have ulcers, whereas the one that seems placid and calm and stands quietly in the back of the stall does."
Andrews suggests there is value in watching a horse eat: "If he eats slowly or eats and leaves the food for a bit, this might hint that the horse has ulcers."
Andrews notes that in people ulcer pain arises predominantly between meals, whereas in horses, stretching of the stomach associated with eating generally is what causes pain. Poor performance has been linked to stomach pain.
McClure says, "Even the selection of your recreational horse can be a risk factor in developing GUS. Choose a calm horse and train it well. The more he gets used to the environments he will encounter in training and competition, the better off he'll be. Commingling with strange horses (ones the horse doesn't know) is stressful, so avoid turning strange horses out together. Also, once social groups are formed, adding or removing horses is stressful."
He concurs on the wisdom of providing a good supply of quality hay, noting, "Free-choice hay or grass is the best antacid there is. Keeping some forage in the stomach to neutralize the acid is beneficial."
Gastric ulcer disease continues to be prevalent in the horse population, regardless of performance level. If there is concern that a horse has gastric ulcers, the typical course of action has been to have his stomach scoped, but another new diagnostic tool is available for stall-side ulcer assessment. A horse suspected of having ulcers should be given a respite from training and competition until ulcer treatment and management changes achieve healing. New medications are available to treat ulcers, and recent research has expanded our understanding about feeding and management practices that help prevent ulcers from occuring.
About the Author
Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.
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