Transcript:

[0:00]

Hi everyone, welcome back to Mad Barn Academy — and if you’re new here, welcome! We hope to earn your subscription today.

[0:06]

I figured it was about time to tackle gastric ulcers, since it is such a common condition and one that our team deals with on a daily basis. Because this is such a big topic, I decided to break it down into a three-part series. Our focus for today will be on the differences between squamous and glandular ulcers, which means we’ll need to cover some background information on stomach anatomy and physiology. In the following videos, we’ll cover diagnosis, treatment, prevention, and dietary management strategies — which is where our nutrition team at Mad Barn really shines.

[0:50]

All right, well let’s get started for today. Equine gastric ulcer syndrome is one of the most common GI diseases or issues diagnosed in horses. We’ll discuss the particulars in more detail soon, but horses have two distinct areas of their stomach: the upper squamous portion and the lower glandular portion. Ulcers can develop in either area — or both, if your horse is particularly unlucky. The reason this is important is because the disease processes are different for these two types of ulcers, which means that treatment is different for each of them. This is why getting an accurate diagnosis is so important: you have to know what area of the stomach you’re dealing with so that you can treat it correctly and address the underlying risk factors to prevent future ulcers.

[1:51]

Most of us horse owners are probably all too familiar with ulcers. Either one of our own horses has been affected, or we know a horse that struggles with a history of ulcers. I know there are a lot of numbers on this slide, but really what I wanted to demonstrate here is just how common both squamous and glandular ulcers are across all populations of horses. For me, the biggest takeaway when sifting through these numbers is that EGUS is extremely prevalent in all populations of competition horses, regardless of discipline or level. EGUS may also be even more common than is documented in our non-competition horses — like our broodmares, pasture pets, or retirees — just due to sampling bias, meaning these horses are probably less likely to be scoped compared to the high-performing athletes.

[2:56]

To understand why ulcers form, we have to first have a basic understanding of the horse’s stomach anatomy and physiology. As I already mentioned, the equine stomach can be split into two distinct areas: the upper squamous portion and the lower glandular portion. You can easily tell these two areas apart when you’re looking at the stomach in real life. The squamous portion, which is labeled “1” in our diagram here, is light pink, while the glandular portion, labeled “2,” is a darker, more purple-pink color. They’re separated by a fold of tissue around the entirety of the stomach called the margo plicatus.

[3:49]

Two other notable anatomical features of the equine stomach are the esophageal opening, labeled “3,” and the pylorus, labeled “4.” The esophagus opens into the stomach at the cardia, and you can actually see the scope coming through the esophageal opening in that upper right-hand picture. The scope comes in, circles around, and gives us that frontal view. The pylorus is the exit from the stomach, where ingesta moves from the stomach into the small intestine. It sits essentially directly below the esophageal opening, under a little shelf or fold of tissue. In the upper right-hand picture, we can’t see the pylorus because it’s covered by that puddle of gastric acid, but if we inflate the stomach with more air during the gastroscopic exam, we can drop down below that shelf — but above the puddle of gastric acid — and visualize the pylorus, which you can see in that lower right-hand picture.

[5:09]

So that’s the big picture — now let’s take things down to the cellular level. The entire interior of the stomach is lined with epithelial cells, which we can differentiate as either squamous epithelium or glandular epithelium, depending on the region. In the glandular region specifically, special cells called parietal cells produce gastric acid — or hydrochloric acid. Horses are interesting because they are basal acid secretors, which means they continuously produce HCl regardless of feed consumption. This differs from other species, like ourselves, which only produce acid in response to food actually entering the stomach.

[6:00]

This is a really important consideration because it means that the glandular epithelium is in contact with hydrochloric acid all the time — which is not ideal. Our cells don’t want to be in contact with a highly corrosive substance day after day. Fortunately, the glandular epithelium has a defense mechanism: the production of a mucus layer that creates a physical barrier protecting the cell surface from harmful gastric acid. Additionally, the epithelial cells secrete bicarbonate ions, which buffer gastric acid close to the cell surface. In this figure, you can see that at the mucosal surface, the pH of the gastric contents is actually very neutral — around a pH of 7, like water — and the farther away you move from the cell surface, the lower the pH gets, until it reaches the pH of hydrochloric acid, which is around 2.

[7:13]

Okay, so now we’re going to take all of that basic knowledge and really apply it to what goes wrong. Why do ulcers actually form, and what happens in the stomach to cause this problem? In the most simplistic terms, ulcers develop due to an imbalance between what scientists have termed mucosal aggressive factors and mucosal protective factors. The aggressive factors are basically all those harsh components of the gastric juice used to initiate digestion — namely hydrochloric acid, but there are a couple of other things in there as well.

[8:00]

The protective factors are exactly what we just talked about — the mucus and bicarbonate layer that sits on the surface of the glandular epithelium and acts as a protective film. On the previous slide, I was very specific about how that mucus layer and the bicarbonate secretion protect the glandular epithelium. That’s because the glandular region is the one that has those defense mechanisms. The squamous region does not — no mucus barrier, no bicarbonate secretion from those squamous epithelial cells.

[8:45]

When we think about what that means and why ulcers form in these different locations, we can start to see why there are two different disease processes, or two different etiologies, for ulcer formation in these two distinct regions of the stomach. Ulcers develop in the squamous portion due to exposure to stomach acid — those cells aren’t meant to come into contact, or at least prolonged contact, with gastric acid. On the other hand, those glandular cells are meant to be in contact with stomach acid day in and day out, so when we get ulcers forming in the glandular portion, it’s because there has been compromise or disruption of those protective mechanisms.

[9:33]

Okay, so let’s talk about risk factors for each of these types of ulcers. For squamous ulcers, we know that prolonged exposure to stomach acid damages the epithelium, erodes those cells away, and creates ulcers. It’s likely that the severity of those ulcers is related to the length of time of acid exposure. Some of the most common or best-accepted risk factors for squamous ulcers include:

• Fasting or inconsistent access to forage between meals — forage really acts as a mat or physical barrier that prevents acid from splashing up onto the squamous epithelium.
• Feeding diets high in carbohydrates or feeding large concentrate meals, which lower the pH of the gastric acid, making it even more harsh and corrosive.
• High-intensity exercise, which increases intra-abdominal pressure and pushes acid up into the squamous portion of the stomach.
• Decreased rate of clearance from the stomach, such as decreased gastric motility or delayed gastric emptying.

[10:55]

For glandular ulcers, we know these form due to disruption or weakening of the protective mechanisms — such as reduced blood flow to the stomach, reduced mucus secretion, and reduced bicarbonate secretion. Risk factors for glandular ulcers include:

• Physical stress or illness.
• Greater than four days per week of exercise, regardless of intensity.
• Inappropriate use of non-steroidal anti-inflammatory drugs such as Bute or Banamine — meaning overdosing, dosing too frequently (another form of overdose), or prolonged use over time.

[11:44]

Okay, that is a wrap on part one of our Equine Gastric Ulcer Syndrome series. In the next video, we’ll move on to diagnosis and treatment. Here are my references for today — I’m sorry the text is so small, but I just had a lot of really good references to list here. I really appreciate you guys taking the time to listen. Don’t forget to like and subscribe, and explore the other videos on our channel. I’ve included links to a few of our blog articles on gastric ulcers in the description below, so feel free to check those out for more information or more detail about gastric ulcers. The next video will be on diagnosis and treatment — that will be part two. I hope to see you back for that. Until next time, thanks everyone!