Why You Don't Spay When the Animal Eats Hay

Anna O'Brien, DVM
By Anna O'Brien, DVM on Aug. 6, 2014

For most people familiar with cats and dogs, the concept of spaying and neutering your pets has been ingrained. For population control, health reasons, and behavioral issues, the reasons behind spaying and neutering our small animal friends are plentiful and obvious. But what about large animals? Spaying of female horses, called mares, is very rarely done. Let’s look at why this is.

To neuter a horse is to geld it and the result is a horse called a gelding. This is the most common surgical procedure done on the farm and most male horses are gelded before they reach the age of three. A relatively simple procedure, gelding can be performed with the horse either heavily sedated and still standing or under general anesthesia lying down.

Most geldings take about thirty minutes from start to finish and the horse can be quietly walked back to his stall to rest. Full recovery in two weeks is common.

The benefits to gelding a male horse far outweigh the risks of infection or anesthesia from the surgery. Non-gelded male horses are called stallions. Stallions can become aggressive and difficult to work with when they reach sexual maturity and recreational horse owners are not experienced enough nor want to deal with the responsibility that comes with owning a stallion.

Spaying a mare is a more complicated medical procedure than gelding, involving entering the abdominal cavity. Although there is more than one way to spay a mare, each resulting in the removal of the ovaries, the procedure tends to be painful and there can be scary complications, such as bleeding from the ovarian artery, which can be difficult to control.

More recently, many veterinarians elect to spay mares using laproscopic methods, which means using small incisions and inserting small cameras on the ends of lasers to view the ovaries and remove them.

Aside from the difficulties of the procedure, many mare owners don’t feel the need to spay their mares because female horses don’t become as aggressive or difficult to work with as many stallions do (I say many, not all, because I’ve known some very pleasant stallions). 

True, some mares are renowned for being somewhat moody, or “mareish,” but some riders actually prefer mares to geldings. My personal opinion is that it all boils down to the individual horse. Yes, some mares are temperamental, but many geldings aren’t perfect either!

Then comes the question of population control, since I feel this is the strongest argument to spay and neuter dogs and cats. Although there is the problem of unwanted horses in the United States, you simply don’t have the hoards of stray horses roaming the streets as you do cats and dogs. Rare is the kid who comes in saying, “Mommy, look what followed me home. Can we keep this horse?”

Additionally, with the majority of male horses gelded, most mares can be kept intact without worries of unwanted pregnancies. Yes, there are stories of a neighbor’s stallion jumping the fence for an amorous visit, but I feel these are somewhat rare.

The primary reason a mare is spayed is due to medical reasons. Occasionally, a mare will develop ovarian cysts or cancerous growths that affect her hormone levels and can make her behave in unpredictable, aggressive, stallion-like ways. If systemic hormone therapies don’t help, removal of the ovaries does the trick.

I think this final observation speaks the loudest as to the rarity of spaying a mare: We were not taught the procedure in vet school. It’s best left to the large animal surgical specialists in veterinary hospitals and referral clinics.

Dr. Anna O'Brien

Image: Horse Crazy / Shutterstock

Anna O'Brien, DVM


Anna O'Brien, DVM


Anna O’Brien, DVM is a large animal veterinarian. A 2008 graduate of Purdue University, she currently works in Maryland, just outside of...

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