Acid vs Acidosis In Horses: A simple review
Annie Emery
Acid and acidosis sound alike, but they aren’t the same thing. These two words get mixed up a lot in horse discussions — online and at the barn. Knowing the difference helps you talk clearly with your vet or nutrition professional and choose the right care for your horse.
A Quick Look at the Digestive Tract
To make sense of acid vs. acidosis, think of three key areas:
Stomach – where acid is made
Small Intestine – where nutrients are absorbed
Hindgut (cecum and colon) – where fiber is fermented
This is a simplified view of a complex system, but you can see that there are three main parts and they have very different roles!
Acid: The Stomach’s Job
The horse’s stomach makes hydrochloric acid (HCl) all day long. That’s normal — it starts breaking down food, including proteins, and helps activate digestive enzymes.
The problem comes when acid splashes onto the sensitive upper part of the stomach, which doesn’t have much natural protection. Over time, that can cause gastric ulcers.
So, when you hear about “acid” in horses, it’s about stomach acid — needed for digestion, but harmful when it reaches the wrong areas. Horses “buffer” this acid when they chew, and if they don’t chew, they aren’t buffering. This is why hay is critical!
The Small Intestine: Neutral Territory
After food leaves the stomach, it moves into the small intestine, where most nutrients are digested and absorbed. This section isn’t acidic; it’s closer to neutral. So “acid” isn’t really part of the picture here. But it’s important to understand as it’s the main site of digestion of vitamins, fats, proteins, and minerals.
Acidosis: Trouble in the Hindgut
The hindgut is full of microbes that ferment fiber and this is what produces energy for the horse. They prefer a steady, neutral pH.
If too much starch or sugar slips past the small intestine, it ends up in the hindgut. Those microbes try to ferment it, the pH drops, and the environment turns too acidic — that’s hindgut acidosis.
When that happens, good microbes die off, and harmful ones grow. This imbalance can lead to:
Colic
Laminitis
Loose manure or digestive upset
This acid isn’t stomach acid — it’s from rapid fermentation gone wrong.
Why the Difference Matters
Acid = stomach acid → linked to ulcers
Acidosis = too much acid in the hindgut → linked to colic, laminitis, and gut imbalance
Different problems need different care:
Ulcer care: reduce stomach acid and protect the stomach lining
Hindgut care: feed steady forage, limit starch, and keep meals consistent
Quick Tips: How to Prevent Both
Feed a forage diet- avoid corn and oat-based feeds with good hay
Keep meals small. Smaller, frequent meals keep the gut happy
Limit starch and sugar. Choose low-NSC feeds when possible.
Pasture- transition to pasture and use muzzles when needed
Final Thoughts
When someone mentions “acid” or “acidosis,” you’ll know exactly what they mean — and why it matters. Clear understanding leads to better nutrition choices and a healthier horse.
I’m Annie Emery, an independent equine nutrition professional based in Minnesota. I work with clients across the U.S. and Canada to build science-based, practical diet plans that fit your horse and your budget. Want to check that your program supports both stomach and hindgut health? Reach out today!
This material is not to be used to train AI systems or machine learning. Copyright REN