Last updated: September 27, 2026
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If your gelding is mounting mares, driving them away from the other horses, or picking fights with the rest of the geldings, you’re probably wondering why he still acts like a stallion and what you need to do about it.
Quick answer: “Proud cut” is an old term for a gelding that still acts like a stallion. Sometimes retained or leftover testicular tissue is still making hormones, but many fully gelded horses just keep learned stallion habits. You can’t tell the difference by behavior alone. Your vet can, with an exam and blood tests.
Here’s what the term really means, why some geldings keep acting studdy, whether he could get a mare pregnant, the signs to watch for, how your vet sorts out hormones from behavior, and what to do once you know.
Table of Contents
What Does Proud Cut Mean?
“Proud cut” is an old barn term, not a medical diagnosis. It describes a gelding that keeps acting like a stallion after he’s been castrated.
For years, people blamed it on a piece of the epididymis being left behind during castration. That theory has been disproven. As the American Quarter Horse Association explains, the epididymis stores sperm but doesn’t produce testosterone, so it won’t make a gelding act like a stallion. Today, when a gelding shows stallion-like behavior, a vet may check for retained testicular tissue, but behavior alone doesn’t tell you whether that’s the cause.
Why Some Geldings Keep Acting Like Stallions
There are a few reasons a gelding can act studdy, and knowing which one you’re dealing with saves you from chasing the wrong fix.
A retained testicle (cryptorchidism). One or both testicles never dropped into the scrotum, and if the hidden one wasn’t found at castration, it keeps making testosterone. These horses are often called rigs or ridglings, though people use those terms loosely.
According to the American College of Veterinary Surgeons, a retained testicle can sit anywhere from inside the abdomen to the inguinal canal in the groin, and it usually has to come out surgically.
Leftover testicular tissue. Less often, a piece of testicular tissue left behind during castration keeps producing hormones.
Learned behavior. A horse gelded later in life, used for breeding, or allowed to practice stallion behavior before he was gelded may keep those habits even when he’s fully gelded. Research backs this up. A 2024 study of geldings reported for stallion-like behavior found that most showed no hormonal sign of leftover testicular tissue.
Horseman’s Take: A testicle that hasn’t descended yet isn’t always a lost cause. I had a colt my vet checked for a suspected retained testicle, and because it appeared to still be coming down, the vet said to wait and recheck instead of scheduling surgery. A few months later it dropped. It took patience, but I was glad I had him checked. The answer came from the vet’s exams, not from guessing.
Can a Proud Cut Horse Get a Mare Pregnant?
Usually not, but some proud cut horses can get a mare pregnant, so don’t assume he’s infertile. Until your vet has figured out exactly what tissue is present, keep a gelding that’s acting studdy away from mares in heat.
A retained testicle usually can’t produce fertile sperm because it’s kept at body temperature, but it can still make testosterone, as the Ontario Ministry of Agriculture explains. That’s why a horse can tease mares, drop, and mount without being able to settle one. Fertility depends on what tissue is actually there, though. A horse with one retained testicle and one normal descended testicle is usually fertile, so if a horse’s castration history is uncertain, don’t take “gelding” on his papers or a seller’s word as proof.
Signs Your Gelding May Be Proud Cut
- Mounting or trying to mount mares
- Strong, persistent interest in mares, especially ones in heat
- Herding or guarding mares in group turnout
- Aggression toward other geldings
- Calling to mares when they’re nearby
- Dropping or erections around mares
Here’s the catch: these behaviors look a lot like plain bad manners. They can raise suspicion, but they don’t prove a horse has testicular tissue. Behavior that’s strongly focused on mares, or gets more obvious around mares in heat, gives your vet useful context. Still, plenty of fully gelded horses act studdy, and a pushy horse may need better handling, training, or turnout management.
Safety note: Handle a suspected proud cut gelding like a stallion until your vet has examined him. Don’t turn him out with mares, don’t hand-walk him near mares in heat, and don’t assume the handling habits that work on your other geldings will hold.
How Vets Test for It
Your vet will start with an exam and then use blood tests to find out whether hormone-producing tissue is still present.
| Test | How it works | What to know |
|---|---|---|
| Baseline testosterone | A single blood draw | Quick and inexpensive, but it can give an unclear answer |
| hCG stimulation test | Blood drawn before and after an hCG injection to see if testosterone rises | Can help clarify an unclear baseline testosterone result, but it takes more than one blood draw |
| Estrone sulfate | A single blood draw | Useful in mature horses, but not recommended in horses under 3 or in donkeys |
| Anti-Müllerian hormone (AMH) | A single blood draw | A strong marker that testicular tissue is present. Your vet may pair it with testosterone testing. |
A single testosterone test can miss some cases, so if the results and the behavior don’t line up, your vet may recommend an hCG stimulation or AMH test. Equine reproduction specialists consider AMH the most useful single blood test for spotting retained testicular tissue. If testing points to a retained testicle, ultrasound can help find it before surgery.
Horseman’s Take: Over 30 years around horses, I’ve seen more than a few geldings called proud cut that were fully gelded and just had learned behavior that needed better handling. Don’t assume surgery is the answer because a horse acts studdy. Get a vet workup first, then spend your money and training time where the results point.
What to Do Once You Have an Answer
| Test result | What usually happens next |
|---|---|
| Retained testicle found | Surgery to find and remove it, sometimes by laparoscopy, by a surgeon experienced with cryptorchids |
| Leftover testicular tissue found | Surgery to remove it, with follow-up testing to confirm hormone levels have dropped |
| No hormone source found | Consistent groundwork and handling, and separation from mares while you retrain him |
Removing retained tissue stops the hormone source, but it doesn’t erase habits overnight. Some horses settle as hormone levels fall, and others still need consistent handling and a setup that keeps them from rehearsing the behavior. If testing finds no hormone source, put your effort into training and turnout management instead of surgery. My guide to building calm, consistent leadership on the ground is a good place to start.
Don’t just live with a confirmed retained testicle, either. Retained testicles are more prone to tumors than descended ones, which is one more reason to have it removed.
Proud Cut Horse FAQ
Is a proud cut horse the same as a ridgling?
Not exactly. A ridgling, or cryptorchid, is a horse with a testicle that never descended. “Proud cut” is the older, broader label for any gelding that still acts like a stallion. A missed ridgling testicle is one of the real reasons a horse ends up acting proud cut.
Is a proud cut horse dangerous?
Not necessarily. Behavior varies a lot from horse to horse, and many can be managed safely with good handling. Still, treat any horse acting studdy around mares or other geldings with extra caution until you know the cause.
Can a proud cut horse be fixed?
Often, yes, but the fix depends on the cause. If your vet finds retained testicular tissue, surgery can remove the hormone source. If testing finds nothing, the horse needs consistent training, safer turnout arrangements, and time away from situations that trigger the behavior. Some horses need both.
Can a gelding act studdy with normal hormone levels?
Yes. A gelding can mount, call to mares, guard them, or act aggressive toward other horses without any retained testicular tissue. Horses gelded later, former breeding horses, and horses that practiced the behavior can keep those habits. If testing rules out a hormone source, focus on training and management, not surgery.
A gelding that acts like a stallion isn’t something to guess about. Keep him away from mares until your vet has examined and tested him, then let the results guide the plan: surgery if retained tissue is there, or steady training and management if it isn’t.
About Miles Henry
Racehorse Owner & Author | 30+ Years in Thoroughbred Racing
Miles Henry (legal name: William Bradley) is a professional horseman based in Folsom, Louisiana. He holds Louisiana Racing License #67012 and has spent over three decades managing Thoroughbreds at premier tracks including Fair Grounds, Delta Downs, and Evangeline Downs.
Expertise & Hands-On Experience: Beyond the track, Miles has decades of experience in specialized equine care, covering everything from hoof health and nutrition to training protocols for Quarter Horses, Friesians, and Paints. Every guide on Horse Racing Sense is rooted in this “boots-on-the-ground” perspective.
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