Castration: The When and How

Advantages to standing sedation castrations include avoiding potential issues associated with putting a horse under anesthesia.

Photo: Bruce Connally, DVM

Science trumps tradition when it comes to gelding male horses.

Most horse industry circles agree: Geld male horses young, unless they are gifted with athletic or genetic greatness and destined for breeding careers. Regarding when and how to do this, however, you’ll find many differences of opinion. Anthony Blikslager, DVM, PhD, professor of equine surgery at North Carolina State University, in Raleigh, says horse owners often base castration approaches on tradition, but he suggests they are are better served by working with their veterinarians to choose the right time and method for each horse. 

When to Do It?

Blikslager prefers to castrate young stallions when they are about 1 year old because he says the surgery is usually simpler and poses less risk for complications than when the horse is older. Mature stallions have larger testicles and blood vessels, which can make the procedure problematic. 

Some owners prefer to castrate horses as foals, which can mean fewer stabling, training, and behavioral issues. Gelded youngsters can be managed together, instead of in separate groups, and are easier to handle than young stallions. Foals also bounce back more quickly after surgery than adults, and their dams help exercise them as they move around the pasture. This eliminates the need to keep the horse active post-castration, as you must do with an older horse. The main disadvantage to castrating horses as foals is they tend to be more prone to developing scrotal hernias.

“Horses castrated as foals generally end up being a little taller than horses cut later in life,” explains Peter Sheerin, DVM, of Nandi Veterinary Associates, in New Freedom, Pa. “The stallion’s long bones stop growing sooner, when he reaches puberty. This is all related to testosterone and closing of the growth plates.” So, the old tradition of waiting until the horse is 2 or 3 years old to geld him so he will “develop” is no reason to postpone castration.  

With regard to time of year, it’s generally best to castrate during cool weather so that flies aren’t present to irritate fresh incisions. Sheerin prefers autumn castrations and also suggests avoiding winter, mainly for veterinarian comfort. “When the temperature is really cold, it’s hard to hold onto instruments,” he says.

Standing Up or Lying Down

Whether performed at a surgical facility or on the farm, there are two ways to castrate horses, explains Sheerin: Standing and sedated or anesthetized and lying down. Both methods offer pros and cons.

With standing castrations, you avoid any potential issues associated with putting a horse under general anesthesia. However, using proper sedation and analgesia (e.g., judicious use of lidocaine) is still important. 

Bruce Connally, DVM, an equine practitioner based in Longmont, Colo., performs both standing and general anesthesia castrations. “Sometimes it’s owner preference, and sometimes it’s my preference,” he says. “If it’s a wild, crazy horse, I won’t do him standing. If it’s a young horse in which the testicles are high and hard to reach, I might also lay that one down.”

But on the whole, Connally says he believes standing castration is generally safer for the horse. “It makes it a little harder for me (in terms of access to the area), but we don’t have to anesthetize him and then get him safely back up without hurting himself,” he explains. “This is why I do a fair number of them standing, and the new (sedative) drugs have made this easier. The biggest disadvantage to standing castrations is the veterinarian’s safety. I’ve never been kicked, but I’ve had a horse kick the emasculator out of my hand while doing a standing castration.”

Sheerin, on the other hand, performs all his castrations with the horse lying down. “That’s just personal preference,” he says. “What I like about the anesthesia is that the horse is down, and if I need to explore something I can do it more readily.”


The Process Itself

When castrating a horse on the farm, most veterinarians prefer to do it in a grassy field or pasture rather than in a stall or on bare ground. It’s cleaner, and the footing provides some give and affords good purchase for when the horse tries to stand (if the surgery is done using general anesthesia).

During castration, the veterinarian makes an incision in the skin over each testicle. Then he or she performs an open, closed, or semi-closed procedure, depending on how he or she plans to negotiate the lining (the vaginal tunic, or “sac”) around the testicle.

“We decide whether we can remove that testicle as is or whether to do the open procedure, which means cutting into the sac around the testicle,” Blikslager explains. “The closed technique is quicker, but the open technique allows for tying off the blood vessels. Most veterinarians make a decision case by case,” based on the size of the blood vessels.

After making the incision(s), the veterinarian removes the testicles using an emasculator—a tool that cuts through the spermatic cord (the tubelike structure comprised of the cremaster muscle, blood supply, ductus deferens, and nerve supply to the testicle), crushing the vessels providing blood to the testicles—as well as 4-5 cm of cord to ensure no testosterone-producing tissue gets left behind. 

“The crushing part is designed to crimp the ends of the blood vessels as they are cut, so they don’t bleed afterward,” says Blikslager. “But after the testicles and blood vessels reach a certain size (in the mature stallion, as compared to a foal or yearling), crushing them is not adequate.” In these cases the veterinarian might need to ligate (tie off) the blood vessels with sutures.

Another consideration to make if castrating the horse under general anesthesia is duration of the anesthesia’s effects. “The standard intravenous technique lasts about 8 to 12 minutes, so we must be quick and efficient,” Blikslager says. “We can redose the horse with anesthetic if the procedure takes longer, but multiple redoses tend to make the recovery from anesthesia rougher.”  

Castration Aftercare

After the procedure the veterinarian and owner must monitor the recovering horse closely. “Bleeding should stop within an hour or two after surgery,” says Connally. “I don’t leave the scene until the horse is done bleeding. There are too many things that might go wrong.” 

Note that you might see dripping for as many as 12 hours or more. “Drips are not a problem, but a steady stream must be halted,” he adds. “Usually the veterinarian will find the bleeder and tie it off, or pack the surgical area full of gauze if he/she can’t find it. Packing puts pressure on the blood vessel and (the bleeding) will stop, and the gauze can be taken out in a day or so.”

Sheerin tells clients to keep the horse confined for the first 12 to 24 hours following surgery to make sure the blood clots well in the area. You don’t want the horse running around—this elevates his heart rate and blood pressure, which could increase the risk of bleeding resuming. After this initial period, however, the horse must get moving.

“The horse needs exercise to prevent excessive swelling and aid … any drainage from the incisions,” says Connally. “(The owner needs) to take him out for 20 minutes at a trot, or lead him three or four miles (at the walk—a walker or longe line is fine, too). Just turning him out doesn’t always work because the horse is sore and doesn’t want to move.” 

Many veterinarians recommend 15 minutes of longeing once or twice a day for two weeks after castration. This will help minimize swelling, which is the body’s normal reaction to injury, and facilitate drainage to reduce infection risk. 

“Some horses appear lame, just because it hurts to advance the leg around the swollen area,” says Connally. “If the swelling goes clear down into their belly they definitely need more exercise.” 

He also emphasizes taking horses’ temperatures daily, noting that if horses have fevers, they need antibiotics.

Managing pain and inflammation is important as well, so that the horse will be comfortable enough to exercise and stave off swelling. Sheerin suggests administering anti-inflammatory drugs flunixin meglumine (Banamine) or phenylbutazone (Bute) for this purpose. 

What Can Go Wrong?

One of the most common castration complications is hemorrhage. To guard against this, it’s important to keep the horse calm and quiet both before and after surgery, for the blood pressure and heart rate reasons described. Veterinarians address hemorrhage by clamping off or ligating the offending vessel.

Callie Fogle, DVM, Dipl. ACVS, clinical assistant professor of equine surgery at North Carolina State University, says normal swelling in the surgical area—starting in the sheath—usually occurs three to four days after the initial surgery. 

“If swelling is in the scrotum, where the testicles were, that needs attention,” says Sheerin. This could indicate a hematoma, infection of the spermatic cord, or hernia.

In most cases veterinarians can treat excessive groin-area swelling on the farm by establishing better drainage via reopening the incision and giving the horse more exercise, as well as administering anti-inflammatories. “Most cases will respond to some combination of these therapies,” Fogle says.

Other signs of spermatic cord infection are fever and anorexia. In such cases your veterinarian should examine the surgical site and can detect the problem using palpation, a white blood cell count, or ultrasound. 

“This is generally a walled-off infection,” says Blikslager. “If it gets up into the cord, it’s like an abscess.” It’s difficult for systemic antibiotics to get into that site.

“This means another, more involved surgery to remove that part of the cord and the walled-off infection,” he continues. “I don’t go through the same castration incision, but make a separate incision, with the horse on his back.”

One of the most serious castration complications is a scrotal hernia, in which the small intestine protrudes into the scrotal sac. Because this can occur following recovery from anesthesia, you need to watch the incision during the first 24 hours for protruding tissue. 

The horse’s omentum, which is made up of fatty yellow tissue that surrounds some of the abdominal organs, also can protrude through the open incisions, but your veterinarian can remove it easily, and Fogle says it’s not a life-threatening situation. 

A protruding part of the small intestine is much more serious. “This is a surgical emergency and life-threatening if not corrected immediately,” Fogle says. “This is rare, but if the owner sees intestines or omentum protruding, they should find a helper and try to clean the tissue as best they can, hold it up, and wait for the veterinarian. The danger when the small intestine starts to protrude is that the horse will start rolling and thrashing because of pain, and more of it will come out,” damaging the intestine. 

Some breeds—those with large inguinal rings (where the inguinal canal, an opening in the body wall through which the testes descend, meets the scrotum)—seem more disposed to herniation than others. “Tennessee Walkers and Standardbreds have more incidence of scrotal hernia,” says Blikslager. There are also family lines in other breeds that develop more of these hernias than what’s considered average.

Take-Home Message 

Our sources recommend castrating every male horse not intended for breeding. Fortunately, this procedure is the most common surgery completed in horses and is very safe—especially if veterinarians perform it properly and the owners monitor and care for horses carefully afterward. A few complications can arise, however, and you should discuss these possibilities with your veterinarian beforehand. 

About the Author

Heather Smith Thomas

Heather Smith Thomas ranches with her husband near Salmon, Idaho, raising cattle and a few horses. She has a B.A. in English and history from University of Puget Sound (1966). She has raised and trained horses for 50 years, and has been writing freelance articles and books nearly that long, publishing 20 books and more than 9,000 articles for horse and livestock publications. Some of her books include Understanding Equine Hoof Care, The Horse Conformation Handbook, Care and Management of Horses, Storey's Guide to Raising Horses and Storey's Guide to Training Horses. Besides having her own blog,, she writes a biweekly blog at that comes out on Tuesdays.

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