When to Geld a Horse - Castration for Colts and Stallions

Updated February 22, 2024 | By: Shannon J. Murray, DVM, MS, DACVS-LA
hunter jumper stallion and show ready rider

Owning a stallion is a huge responsibility and often not the best situation for the majority of horse owners. Choosing to castrate your horse has many advantages and knowing what’s involved in the process can help you make the best decision at the right time. Learn when and how it’s done, along with tips for caring for your newly gelded horse while he heals.

What Does it Mean to Castrate Your Horse?

Castration refers to the surgical removal of a male horse’s testicles. Once a colt or stallion is castrated, he is referred to as a gelding. This is one of the most common surgeries in equine medicine and is also referred to as emasculation, gelding, or cutting.

Why Geld Your Colt or Stallion?

Castration is often performed to:

  • Minimize unwanted stallion-like behavior, such as displays of sexual interest in mares, mounting, or an aggressive temperament toward other horses and/or people.
  • Prevent unwanted pregnancies if a horse is not intended to be used for breeding.
  • Make a horse easier to manage for training and stabling. (Stallions require knowledgeable handlers and specific housing, fencing, and turnout.)
  • For medical reasons, like trauma to the testicles or spermatic cord.
  • Prevent overbreeding, and in turn, promote equine welfare by reducing the number of horses in need of homes.

The castration procedure may be delayed:

  • When the owners desire the stallion-like physical attributes, such as a well-muscled body or thick, cresty neck, which develop under the influence of testosterone.
  • To determine if a horse is suitable for breeding.

Castration is often not performed:

  • If a horse is intended to be bred.

When Should a Horse be Gelded?

well muscled stallion like bay horse with owner

It’s most common for colts to be castrated between 6 months and 2 years of age when they’re not intended to become breeding stallions. This traditional timing is aimed to be before puberty in the hopes of preventing him from developing unwanted stallion-like behavior.

There is currently little research for castrating colts earlier than 6 months of age. However, one study published in 2022 looked at a herd of Welsh Ponies and compared the effects of early castration (3 days old) versus traditional castration (18 months old). They did not find early castration to interfere with physical or behavioral development. More research is still needed to look at other parameters that could be affected by early castration [1]. Medical concern for castrating a horse earlier than 6 months of age are unapparent inguinal hernias, but most tend to resolve by 3 to 6 months of age [2].

Castrating after puberty, within the time frame of 2 to 4 years old, is often performed when owners want the stallion-like physical attributes, including a well-muscled body and a thick, cresty neck.

Castration does not guarantee your horse won’t act like a stallion and display typical unwanted behaviors, especially if he has bred mares or is older. This type of behavior will likely continue after he is gelded as they’re usually learned traits. Research has shown that 20 to 30% of castrated horses continue to display interest in mares and aggression towards other horses. About 5% even continue to show aggression towards people [2].

Ask the Vet Video on When to Geld a Colt

SARAH: "What is the best age to geld a stallion? Is it better to do before starting them under saddle?"

This is so interesting because I was at my mother in law's house and we had a question about the different sexes of horses.

DR LYDIA GRAY: Where are you going with this? OK.

SARAH: We had stallions, and geldings, and mares because she just got a rescue dog and they apparently did his neuter the way that you neuter a cat, not the way that you usually neuter a dog. Which is different, which I didn't know. Anyway.

DR LYDIA GRAY: I'm like, was there are a question?

SARAH: Nope. Just talking a lot about gelding.

DR LYDIA GRAY: Getting back to the gelding question. So I have a funny story.

SARAH: Yes.

DR LYDIA GRAY: When I was in practice, I had a request from a client to geld a really, really, really, young horse. A foal.

SARAH: Oh.

DR LYDIA GRAY: And I had never been asked that before, and they didn't teach me that in vet school, so I called up a local practitioner who was more experienced, had been around. I told him what was going on and he said, "Well, are all four legs out?" I said, "Out of what?" He said the uterus. I went well, yeah. So that's--

SARAH: So there's apparently no age too young.

DR LYDIA GRAY: --the answer.

SARAH: Wow.

DR LYDIA GRAY: There's a lot of--

SARAH: Good question.

DR LYDIA GRAY: --misconceptions about it. I go online and I Google and I read people. People think, and there's a lot of people who think, oh I have to wait till my colt drops before he's gelded. Well, here's the facts. Science wins. The testicles of the horse drop between 30 days before birth and 10 days after birth.

SARAH: That's why, hence the question.

DR LYDIA GRAY: Yeah. Then the ring that allows them that they drop through, closes.

SARAH: Inguinal ring.

DR LYDIA GRAY: Yeah.

SARAH: I know.

DR LYDIA GRAY: Ding, ding, ding.

SARAH: Thank you.

DR LYDIA GRAY: That's later. The inguinal ring closes and then they're either dropped, or they're not dropped. You do not have to wait for that to happen. Now, if they're not dropped or maybe one's not dropped, then the horse has cryptorchidism, which is a separate deal and you can't castrate in the field. The horse has to be taken to a surgical facility. That misconception we can just throw out the window today.

The horses, so horses reach sexual maturity, or puberty, at 18 to 24 months. Most people want to, if they know they're not keeping the horses as stallions they want to, geld before then. I would say a year. Six to 12 months is kind of what most vets will do because it's actually a lot easier the younger they are. The horse is not as big. There's less bleeding, all the tissues are smaller, they get up from the anesthesia better, they just heal better. There's less trauma.

One of the things I hated to do in practice was someone would bring me a 10, 15, 20-year-old stallion, breeding stallion even, and say we're done. We want to castrate him. And I'm like, oh this is going to be a nasty surgery. There's lots of reasons to castrate them early. One is, tell me if you know this, if you castrate a male horse before they reach sexual maturity they will be taller.

SARAH: Really?

DR LYDIA GRAY: I'm going to go with no you didn't know that.

SARAH: Yeah.

DR LYDIA GRAY: Testosterone delays, or it actually enhances the closing of the growth plates. If you get that hormone out of the system, the growth plates close when they naturally should. So when you see stallions that might be 16 hands 16-2, and then a gelding out of that same stallion is 17 hands 17-2.

SARAH: Interesting. I had no idea.

DR LYDIA GRAY: That's one consideration is how tall do you want the horse. How masculine do you want the horse to look. Some don't like to geld young because they want to see performance.

SARAH: That was going to be my other question. Is it-- because the tallness you would kind of think is the opposite but that was interesting and so I wondered-- are there things like the way that stallions present themselves? Do they always have nicer manes, or is that just my impression?

DR LYDIA GRAY: It's probably the crestiness of their neck that makes their mane look so-- as far as presence there is definitely a stallion presence, yet there are many geldings that are pretty sure they're hot stuff. I don't know that you need-- that's not for me one reason to keep horse a stallion because there are lots of cons to keeping a stallion. You not going to be able to turn out in a group, especially a group of females. Lots of barns prohibit you from being there. We don't want stallions. A junior can't show a stallion in many disciplines. There's just a lot of reasons to not having a stallion.

Unless the horse has superior breeding lines, or really good way of going, or you want to keep him as a stallion, I would geld. I would geld young. Get it done.

Cryptorchidism

For most horses, the testicles normally descend into the scrotum during the last 30 days of gestation or within the first 10 days after birth. When one or both testicles do not descend into the scrotum, it’s referred to as cryptorchidism. Colts or stallions with cryptorchidism are also called high flankers, rigs, ridglings, or originals.

It is more common for one testicle (unilateral) to be retained than for both (bilateral). Breeds that have a higher incidence of cryptorchidism include Percherons, Quarter Horses, Saddlebreds, and pony breeds.

The Castration Procedure

Before surgery, it is important to have your horse evaluated by a veterinarian for a full physical exam. Depending on your horse’ behavior, your veterinarian may administer sedation to palpate the scrotal and inguinal regions. This is performed to determine if both testicles have descended, which is key in determining the surgical plan.

There are a few different castration procedures that can take place depending on what your horse needs. If both testicles have descended, then the castration can take place either with the horse under intravenous anesthesia (most commonly performed) or standing under sedation. For routine castrations, there are three surgical techniques – open, closed, and semi-closed.

Routine castrations can take place at your farm if there is a clean and safe area to anesthetize and recover your horse from sedation. Oftentimes your regular veterinarian is experienced in this and can perform this procedure. They will determine what medications to give your horse, such as antibiotics and pain relief. Your vet may also give him a tetanus vaccine if he’s not current or has not had one within 6 months of the procedure.

The surgical incision in the scrotum is usually left to heal on its own and not sutured closed.

Recovery Time and Aftercare

  • Exercise (turnout, in-hand, or undersaddle) must be restricted for the first 24 hours post-surgery.
  • After the first 24 hours, it’s important that your horse is exercised to reduce inflammation and encourage drainage. Your vet may refer to this time as “forced exercise,” which they will define for you, but typically includes hand walking or trotting for 15-20 minutes twice daily for 10 to 14 days. Turnout alone cannot guarantee that your horse will get enough exercise.
  • Your horse should be isolated from mares for at least 14 days following castration [4]. After this time, they are unlikely to impregnate a mare.
  • The castration site should heal by 3 weeks if no complications.

Potential Post-Operative Complications

Edema

Swelling in the region of the scrotum and prepuce can be normal following surgery and is greatest around day 4 or 5. Excessive edema, however, is the most common complication following castration. Excessive edema can result from a lack of vigorous exercise, a lack of drainage from the wound healing too soon, and/or an infection. There are reports that older horses are more prone to developing excessive edema than younger horses [3]. Contact your veterinarian if he has excessive swelling.

Hemorrhage

Some bleeding is expected after surgery. However, if the drops of blood from the surgery site cannot be counted and continue at a fast drip to steady stream for more than 15 minutes, veterinary intervention needs to take place.

Infection

Clinical signs of an infection can include but are not limited to:

  • swelling of the scrotum/prepuce
  • drainage from the surgical site
  • fever
  • lethargy
  • not wanting to walk

An infected scrotal wound can be referred to as septic funiculitis. Antibiotics prescribed by your veterinarian may resolve the infection. A chronically infected stump is called a scirrhous cord. Removal of the infected tissue is usually required at a hospital by an equine surgeon. Contact your veterinarian if you have any concern about an infection and they will guide you in the next steps.

Continued Unwanted Stallion-Like Behavior

quarter horse stallion trotting outside
Image courtesy of Alana Harrison Photography.

Stallion-like behavior continuing after castration reflects a learned behavior. Castration does not always eliminate unwanted behaviors. Geldings that maintain stallion-like behavior can be referred to as false rigs.

Hydrocoele

Hydrocoele is a fluid accumulation within the scrotum that’s more often seen in mules than in horses. This may appear in a gelding months or years after castration. If the hydrocoele does not appear to bother the horse, is not cosmetically displeasing to the owner, and does not increase in size, no treatment is necessary. Otherwise, they can be removed by your vet.

Evisceration

This is when a portion of the intestine or omentum prolapses from inside the abdomen out through the scrotal incision. The risk of evisceration is very low. However, it is considered a true emergency when it happens. You will need to keep your horse quiet and contact your veterinarian immediately. Draft horses and Standardbreds may be more at risk for evisceration due to their having a higher incidence of congenital inguinal herniation. Concern has also been raised for Tennessee Walking Horses and American Saddlebreds being at increased risk.

Average Cost of Gelding a Horse

A survey of equine veterinary fees shared by the AAEP (American Association of Equine Practitioners), shows that the price for gelding a horse can vary, but on average the cost is:

  • $328 for a routine castration (standing procedure)
  • $335 for a routine castration (recumbent procedure)

According to the author’s sources, costs for a cryptorchid castration can vary from $1,300 to $3,400 depending on the type of veterinary practice and its location.

Please note that these costs are solely for the procedure and do not include other costs that your veterinarian or equine hospital may charge.

Evidence-Based References

  1. Cognie J, et al. Early Castration in foals: Consequences on physical and behavioural development. Equine Vet J. 2023;55:214-221.
  2. Schumacher, J. (2012) Testis. In Auer and Stick, Equine Surgery (4th ed., pp. 804-840). El Sevier Saunders.
  3. Kilcoyne I and Spier S, Vet Clinic Equine 37 (2021) 259-273. http://doi.org/10.1016/j/cveq.2021.04.002
  4. Castration: From stallion to gelding. American Association of Equine Practitioners. (n.d.). https://aaep.org/horsehealth/castration-stallion-gelding
SmartPak Equine™ strongly encourages you to consult your veterinarian regarding specific questions about your horse's health. This information is not intended to diagnose or treat any disease, and is purely educational.