When Horses Stress Out: Gastric Ulcers, Part 1
It’s amazing how many medical similarities humans share with our domesticated animal species. You and I get influenza and so do our swine friends. You and I get cancers like melanoma and lymphoma and so do our horses and cattle. You and I also get stressed and so do our pets. Flare-ups of gastric ulcers are one clinical manifestation of stress in humans and interestingly enough, our equine and bovine compatriots can suffer from these stomach pains as well. Let’s take a closer look at ulcers in our large animals.
Gastric ulcers occur primarily when acidic stomach juices containing primarily hydrochloric acid overwhelm the production of protective mucus along the lining of the stomach. When the highly acidic gastric juice comes into contact with unprotected areas of the stomach lining, the delicate gastric epithelial cells are damaged, leading to ulcer formation.
There are many factors contributing to gastric ulcer formation in horses. One common cause of gastric ulcers in this species is related to gastric emptying time. Studies have shown that horses fed only grain without roughage such as hay have extremely quick gastric emptying times. This results in the exposure of the walls of the stomach to gastric juices without the buffer of feed materials. Horses on pasture and those fed large amounts of hay have lengthy gastric emptying times, and also lower rates of gastric ulcer formation.
Environmental stressors can also predispose a horse to gastric ulcers. Merely being kept in a stall versus turned out in a pasture is a risk factor, as is heavy performance demands. Studies have shown that up to 90 percent of racehorses have gastric ulcers, and 60 percent of show horses suffer as well. Although some of this is due to diet (high grain diets are fed to high performing horses to ensure adequate caloric intake) and housing (many racehorses and high end show horses are kept in stalls during their careers), it appears that high intensity physical stress also adds to gastric pathology.
Certain medications are known for increasing the risk of gastric ulcer formation as well. Common non-steroidal anti-inflammatory drugs (NSAIDs) used in horses such as phenylbutazone (tradename Bute) and flunixin meglumine (tradename Banamine) are used very frequently in horses for lameness issues, colic pain, fever reducers, and other common maladies. These drugs act negatively on certain hormones that regulate gastric acid secretion. The same thing is seen in humans taking aspirin.
So how do you know when a horse has an ulcer? Many mild ulcers go undiagnosed. For more severe cases, a horse may exhibit decreased appetite, weight loss, rough coat, decreased performance, teeth grinding, and even mild colic signs such as lying down, looking at the flank, or playing in the water but not drinking. Basically, they just don’t look like they feel good.
Confirmatory diagnosis can only be made via endoscope. Some on-farm practitioners, especially those specializing only in equines, will have one (I don’t); otherwise most large animal hospitals will have one. Inserted up the nose and down the esophagus, visualizing a gastric ulcer via endoscope is sometimes pretty dramatic. There’s nothing like a violent-looking angry red blotch on an otherwise smooth, pink stomach lining to show owners, “Lookie here, this is why Thunder doesn’t feel so good.”
Luckily, there is treatment for gastric ulcers in horses. Called GastroGard, this drug is omeprazole, the same anti-ulcer medication given to humans in the “purple pill” called Prilosec. (It’s funny to me when animal and owner find themselves on the same medication. I find it creates a certain bond.) Referred to as an “acid-pump inhibitor,” omeprazole decreases the stomach’s overall production of gastric acid. Given orally, this medication is effective in healing a horse’s ulcers and also in preventing formation of new ones. Obviously, to further help mitigate ulcer formation, environmental changes such as feeding and housing should be addressed as well.
Next week we’ll look at the hows, whys, and whats of gastric ulcers in cows.
Dr. Anna O'Brien