This is a much debated and frequently asked question. It is also with many possible answers. Honestly, there are many factors that go into this decision and there is no one absolute answer. I will, however, discuss some factors and reasons why one should do so and when.
Let me start by saying the age at which it is recommended that an animal be spayed or neutered is a case-by-case evaluation of environment, breed, purpose of use, and disease prevention. All these factors go into a sort of risk assessment analysis and we come up with a recommendation.
There are many opinions about this topic and each person’s feelings about this topic can be very emotionally charged and staunchly entrenched. Do not assume that one person is right, and everyone else is wrong.
Now, lets get down to the question at hand. When I am in an appointment with a client and their puppy, I ask them the initial question of, “Do you plan to breed him/her or do you plan to have them spayed/neutered”? If the owner has a definite answer, then I know where to take the conversation. If they plan to breed, I let them know about the risks of breeding and pregnancy and what to do when they decide they no longer want to breed them. Sometimes, this is enough to change their minds. At other times, they have already considered these factors and feel they are prepared. I always make sure they know the signs to watch for in the event of pyometra. This is a life-threatening uterine infection that can result even if the female is not bred. Simply going through a heat cycle can set up the cascade of steps that occur in creating this infection. The only real treatment for this is to be spayed. Sometimes on an emergency basis.
Rescue groups, shelters and humane societies often have their adoptees spayed or neutered incredibly early in their young lives. Sometimes as early as 8-12 weeks. This is coming from a very narrow perspective of strict population control. I get their point of view, but I do not have to focus solely on that in my practice with my clients. My youngest limit is 6 months of age. I do not like to spay/neuter prior to that date regardless of the breed or situation. I feel that it does put the individual in a compromised circumstance and may create more problems later than it prevents.
It is true that breed plays a factor. There are recent studies that show that it may be more than just size of the breed at maturity that is a concern. Dachshunds are prone to back problems and neutering them prior to 12 months (or some cases, 24 months) can greatly increase their chance of having a major back injury during their life. Larger breed dogs, structurally mature later in life and should be allowed to grow and mature with their hormones intact. Everything from joint health and cancer prevention can be affected by sex/growth hormones during the developmental period. I waited to spay and neuter my larger breed babies at 12 months.
In terms of cancer prevention, you can also prevent certain types of cancer by spaying/neutering prior to a certain time. Case and point is the prevention of mammary carcinoma in females. Spaying dogs prior to their first heat cycle can prevent mammary carcinoma by almost 90%. If you wait until after the 2nd cycle, the prevention drops to 75%. After the 3rd or subsequent cycles, it is even less.
Male dogs have the added concern over inappropriate or undesired behavioral concerns. You may have to balance the concerns with disease prevention and bad behavior. Sometimes you have to make a less than ideal decision because the pet is exhibiting some other problem that changes the timetable.
Of course, I cannot have this conversation without mentioning the pregnancy factor. Undesired litters happen all the time. Many of these puppies and kittens end up with poor if not desperately short lives. If you are not going to breed and accidental breeding is possible, please spay or neuter.
So, bottom line, you need to consider all the factors discuss those factors with your vet and then make the best choice for you and your pet. We will happily have this conversation with you any time.