By Mary C. Wakeman, D.V.M.



Politically correct conventional wisdom is not necessarily biologically correct. Also, old wives tale regarding testicles and behavioral matters are often just that.  The only true justifications for castrating dogs are

1) aggressive behavior toward other dogs in the same household

2) perianal adenoma in old dogs.

Aggression to other dogs in situations outside the house is pretty normal dog behavior.


Appropriate behavior.  Since your dog will be on lead or inside a secure fence at all times, there should be no problem with dogs outside your household.  However, if male house mates fight, and both need to stay with you, castration of one or both may solve the aggression problems.  If you fault your dog for being aggressive to acquaintances while being walked on lead, you should not.  He is guarding you.  That is simple.


Honorable behavior.  If your dog is aggressive in a 'dog park' where he is running free, or on the beach, or in the woods, or otherwise neutral territory, you need to do more training or keep him on leash.  Dogs that can manage such encounters without aggression are fine, but you cannot automatically expect an unknown dog to have friendly relations with animals from outside his own 'pack'. It goes against his whole evolution.  


Perianal adenomas, benign but messy tumors in old dogs may be treated by castration.


In terms of your dog's health, two overriding concerns are present. Castration at an early age will cause the dog to become overly tall, as the growth plates in the long bones will not close at the appropriate time; additionally, the dog will lack breadth of chest.  The combination of these two factors sets the stage for your dog to have painful orthopedic problems. The OFA has published articles on this subject.  An early age means below 1 year in small and medium sized dogs, and below 2 to 2.5 years in large and giant breeds.  The statement that your dog will not automatically gain weight is rubbish.  Removing sexual hormones will change his metabolism and make your dog more sluggish, resulting almost inevitably in weight gain.  Also, muscle tone will decline after castration, and the classic result of this is a fat dog in poor muscle tone that ends up having a cruciate ligament rupture in the knee.  Can you avoid the consequences to weight and condition?  Sure in the ideal world it's possible, but in the real world, the overwhelming percentage of owners do not succeed in this endeavor.


The second concern regarding your dog's health is highly malignant prostate cancer.  Virtually all malignant prostatic tumors in dogs occur in castrated dogs.  Castrating your dog puts him at risk for one of the worst cancers he can get.  While you remove the very slight risk of testicular cancer in castrated dogs, that's a small matter; the incidence of testicular cancer is so minimal.  Also, almost all testicular cancers in dogs are benign.  If we find a testicular tumor, we normally remove the testicle with the mass and leave the remaining one intact.  The relative incidence and severity of the tumors of the prostate relative to tumors of the testicle make the decision to keep your dog intact a virtual no-brainer.  The information on the incidence of prostatic malignancies was obtained through a very large study of the records at veterinary colleges. These findings have been published for several years.  Infection or inflammation of the prostate may occur in intact male dogs that are chronically exposed to bitches in heat.  These are often worrisome to owners who seem to confuse prostatitis with the more serious prostate cancer.  Prostatic infections are easily treated, and not, per se, a reason for castration.  So, the bottom line is:


1. Never castrate your dog because it is Politically Correct


2. Only castrate your dog if his home life is at risk due to dog- to-dog aggression, or if, at the age of 11 years or so, he develops a perianal adenoma.