A topic that is getting much debate now is about if/when to get your pets spayed or neutered.

First – let us specify the difference between spaying and neutering. Typically we say you neuter(castrate) a male animal and you spay(ovariohysterectomy or ovariectomy) a female, but you can use “neuter” interchangeably.

Now, why do we push so hard for spaying/neutering pets in the first place? The main reason is just like Bob Barker used to say, “help control the pet population.” We have all seen overcrowded shelters and heard the numbers of animals being euthanized because we can’t find them homes. If more animals are spayed/neutered we will help to control that overpopulation. There are a few more reasons that we will discuss towards the end, but first we will discuss some studies people may quote against and for spaying.

Within the last handful of years, a couple of studies have come out discussing the “risks” of spaying/neutering our pets. Most of these studies were just in dogs. The first study that everyone quotes was done in Golden Retrievers(click here for that study). They discuss different types of cancer, a joint issue and cruciate(ligament in the hind limbs) injuries. Most of these issues were more prevalent in the neutered animals but I feel it depends how you think about the study. It is “statistically significant”(which means the chance of the result being random is unlikely), but I don’t feel it is a large difference. A great example of this is the hemangiosarcoma(tumor of blood vessels) in female dogs. The study had 2/123 intact dogs diagnosed with this tumor and 3/170 neutered early dogs diagnosed with this tumor. This 1% difference was found to be “statistically significant.” I would not be confident saying a spayed female is more likely to develop this type of cancer. If we had 50/170 of these spayed dogs getting this cancer while only 2/123 intact developed this cancer that would carry much more weight. Anything can look impressive on a bar graph if you space it out enough.

Another lifespan study here looks at cause of death for intact for neutered animals. This study found that neutered animals lived longer than intact animals. The intact animals died from trauma and infectious disease more than the neutered animals. They also found that the neutered animals developed cancer more than the intact animals, however, the neutered animals were living longer. This would make sense as intact animals are more likely to try and escape and roam and neutered animals don’t care about traveling around to find a male/female to breed with.

These studies are also discussed in another post by another DVM here.

Now, after these few studies I will give my personal opinion about spaying/neutering canine/feline pets.

Cats: Spay/Neuter all cats. It’s very easy for cats to escape and it only takes once for them to become pregnant. There are also infectious diseases that can be spread through mating. Male cats have a higher tendency to spray(mark territory) in the house and I know that is a quick way to cause an owner to surrender a cat or kick them outside. We don’t have good studies for felines about spaying/neutering but we do see plenty of 18-19 year cats that are spayed/neutered.

Dogs: Spay all females, males can be discussed.

Female dogs – There are two main reasons I push hard for females to be spayed: Pyometra and Mammary Cancer. A pyometra is an infection in the uterus that can occur after the dog comes out of heat(their “cycle,” usually every 6 months). So, each time she goes into heat, there is a risk of this infection. This can be a life threatening infection. If the infection becomes trapped in the uterus, it can cause it to expand until the uterus ruptures. If you properly remove the ovaries, this risk of this condition is significantly decreased. Next, dogs that are intact or even spayed at a late age (>1 year old), have a higher risk of developing mammary cancer. These are masses that can be pretty big and can involve the entire mammary chain. Removal sometimes involves taking the majority of the mammary chain which means a very large incision and increased complications. This cancer can spread throughout the body also. If dogs are spayed before their first heat, mammary cancer is nearly 100% eliminated.

Male dogs – I agree with either decision on males. Reason not to neuter: maybe the testicles help with certain issues. For example, I do believe it helps to keep them lean and not get fat as easily. Different concerns with leaving them intact include testicular cancer/atrophy(shrinking down) as they age, if this occurs we just neuter and send the testicles out for biopsy to see what’s going on. A neuter is a pretty easy/quick procedure. With bigger, older dogs, we may recommend a scrotal ablation with the neuter. This is where we remove the excess tissue that is left behind when removing the testes as this skin will very likely fill with fluid and cause discomfort after the surgery. The main reason to neuter is more behavioral. As discussed in with the earlier study, in tact males are more likely to roam, especially if they smell a female in heat. These dogs may escape and then get hit by a car or get into a fight. Intact males are much more likely to mark(although neutered males may mark some).

What Age to Neuter/Spay:

I like to neuter/spay all dogs and cats around 5-6 months. I want to catch them before their first heat and I also want to give them some time before removing those hormones. Some people will push to wait for large breed dogs sometimes up to 18-24 months! I don’t feel we have any good evidence that waiting that long needs to be done. I also feel the surgeries are more difficult the bigger/older they are.

Bottom Line:

For me, the bottom line is around 5-6 months to spay all dogs/cats, neuter all cats and recommend neutering male dogs but I don’t push as hard for that as long as you can keep them confined and train them properly.