It only when they are spayed or neutered before they are finished growing...the growth plates dont close when they are supposed to because there are no hormones telling them when to close
These are from the latest issue of Veterinary Practice News (Aug 2005). Summarized by a vet on the beardielist: We are mostly aware that spaying a bitch before her first season halves her risk of mammary cancer, and obviously castration frees you from concerns about testicular cancer, which is particularly worrisome in boys with retained testicles, but what about other cancers? Here are some figures that may surprise you. Spayed bitches had four times the incidence of cardiac hemangiosarcom as compared to intact bitches. Neutered males have a significantly greater risk for these tumors compared to their intact brethren. Prostate cancer is four times more common in castrated dogs compared to intact ones. Neutered and spayed dogs have up to 3 times the likelihood of developing bladder cancer compared to intact ones, and are twice as likely to develop osteosarcoma (bone cancer). Males are four times more likely to die within 2 years of diagnosis when compared with females. Dogs neutered or spayed before they were a year old had a one in four lifetime risk of getting osteosarcoma. Ultimately, with the unfolding of the canine genome, we may know which cancers our dogs are most likely to get, and be able to say whether an individual is better intact or neutered, in the meantime, as with most questions, the answer to whether spaying or neutering is better from a health point of view is "it depends."