It seems de-sexing a male dog will assist in preventing undesirable behaviors that can surface with an entire male dog; for example aggression, roaming, cocking the leg to urinate.

Is this true?

If so what is the optimal age to de-sex a male dog to help prevent the onset of such behaviors?

  • Recommended age of 6 months old or any time after the dogs testicales have descended. Generally neutering or spaying will change the dogs excitement levels but any habits it has learnt might, but not always stay with them. If you really want your male dog to be calmer, not wee all over and not chase bitches, then 6~8 months.
    – Piotr Kula
    Commented Feb 27, 2014 at 15:45

5 Answers 5


For male dogs, it doesn't seem to matter. Some behaviours will respond to castration, others won't, no matter the age of the dog:

Castration was most effective in altering objectionable urine making, mounting, and roaming. With various types of aggressive behavior, including aggression toward human family members, castration may be effective in decreasing aggression in some dogs, but fewer than a third can be expected to have marked improvement. Age of the dog or duration of the problem behavior does not have value in predicting whether castration will have a beneficial effect. (Neilson et al., 1997)

For female dogs, however, it seems that spaying them to early is associated with an increased risk of urinary tract infections:

Because earlyage gonadectomy appears to offer more benefits than risks for male dogs, animal shelters can safely gonadectomize male dogs at a young age and veterinary practitioners should consider recommending routine gonadectomy for client-owned male dogs before the traditional age of 6 to 8 months. For female dogs, however, increased urinary incontinence suggests that delaying gonadectomy until at least 3 months of age may be beneficial. (Spain et al., 2004)


  • 1
    It definitely matters for long term health of the dog. There are reasons why you might want to do it earlier or later but they both have potential negative and positive consequences.
    – Beth Lang
    Commented Mar 4, 2014 at 6:29

For performance dogs we like to wait until 18 months on average. The point is to wait for them to really be done growing. Removing hormones before that point can cause bones and muscle to grow differently than they would have otherwise. Dogs fixed early tend to be taller and less filled out than they would have been otherwise. However if it is a non - working pet dog than the difference is not likely to matter too much. And for males, if you are seeing unwanted behavior you will have to weigh your options. If you are seeing aggression, obsessive marking, or wandering and you don't feel that you can overcome these behaviors with training then you may want to fix your dog earlier than the 18 month mark. Also, if you have both an unfixed male and female and you don't intend to breed then do yourself a favor and fix at least one of them... it can be incredibly difficult to keep them separated enough during the females season to prevent an accidental breeding.

If it is a large breed or a breed prone to hip dysplasia I would wait for the 18 month mark at minimum even if the dog wasn't in a sport. I've been training and competing in dog sports for 10 years and I think it is actually pretty amazing that just from the look of a dog you can often guess if they were fixed early but that is just an observation, for the real data...

This is a good paper that sites several studies done that found increased incidents of CCL rupture, hip dysplasia, and patellar luxation in dogs that were fixed early. These injuries seem to correlate with the findings of longer tibia, radius and ulna which are likely caused by the delayed closure of growth plates. The lack of hormones slows the closure and allows the bones to grow longer than they would have otherwise. This results in dogs that are taller and don't have as deep of chest cavities as they would have otherwise.

It looks like the bones may be less dense than they would have otherwise as well but I have not yet found a scientific study to back that up.

I think it is really encouraging that we are now seeing alternatives to a full spay or neuter that keep some or all of the hormones without the risk of accidental breeding. Some of the alternatives are ovarian or uterine sparing spays and for the boys there is now a product called Zeuterin. If these catch on it's possible that we will see the rate of these injuries decrease significantly.

  • I'm considering neutering my dog but wanted to get back to your answer first. I thought you advised to wait for him to be at least 2. He's now 21 m/o.
    – Cedric H.
    Commented May 24, 2015 at 18:05
  • 1
    I would not worry about it at all as long as they are over 18 months. Unless it is a giant breed then I would wait longer assuming there are no behavior issues.
    – Beth Lang
    Commented May 27, 2015 at 7:01

I am not sure about optimal age... But I know that even at 8 years old, dogs still may show a change of behaviour.

Just to add to your thoughts, mine is 9 months old, it has been 1 month since the operation and he changed to all what people lead us to expect.

He was very dominating, and if we refused him something he would let us know (We mainly invited that to happen in the first place as we did not know how to take care of a dog). Now he is still protecting the house but is very gentle with us.

Some say the younger the better, and that 5-6 month is best, but we wanted to wait for him to "man up" a bit first... Don't know if it changed anything.

Other question to ask yourself, is it a working dog? I doubt you'd desex a guard dog for instance.


There's an answer to this on Cesar Millan's website from a vet.

In short, some studies have shown a link between neutering a dog before 14 months of age and cancer/joint problems and other studies show benefits in early neutering.

Edit: Here are a few more articles from the same website on spraying and neutering.


It can can bring about a change behavior, but in our Collie-cross' case, it hasn't changed his behavior one bit (apart from not cocking his leg).

I guess the optimum age really depends on each individual case.

In any case, the minimum age you can desex a male dog is 8 weeks. Most vets will recommend waiting until at least 6 months.