While neutering may be beneficial from the standpoint of fewer dogs in rescue, for the individual dog, it may be worth taking a second look at the common practice of neutering all male dogs not in the AKC show ring.
In the 5th ed of Ettinger  Textbook of Veterinary Internal Medicine it says; “The risk of prostatic carcinoma in a castrated male dog is approximately two times greater than the risk in an intact male dog, and the risk appears to increase with the time that the dog has been castrated.  A dog that has been castrated for at least 10 years has a four times the risk of developing a carcinoma as an intact dog.”
“The cause of canine prostatic carcinoma is unknown, although castration and increasing age appear to increase the risk. [5, 6]” Various studies have found different incidence of prostatic carcinoma, which, is generally of low prevalence in dogs. eg 0-0.6% of all necropsies . However, in dogs presenting with prostatic disease, incidence increases — eg 13%-20% of all prostatic disease cases [3,7].
With regard to cancer, spayed females have a four-times greater risk for developing cardiac hemangiosarcomas (vascular tumors) compared to intact females (neutered males also show a significant increase in risk for these tumors compared to intact males) Ware and Hysper, J. Vet. Intern. Med. 13:95-103, 1999.
Additionally, both neutered males and females have a two-fold greater risk for developing bone tumors (osteosarcoma) compared to intact males and females (Ru et al., Vet J. 156:31-9, 1998.)
Some evidence suggests that early neutering may also predispose to endocrine disorders later in life (Panciera DL. J. Am. Vet. Med. Assoc., 204:761-7, 1994.).
Furthermore, there is also an indication that early neutering (because absence of sex hormones delays maturation of osteoclasts and thus results in delayed closing of the growth plates in the long bones) may predispose to increased risk for various orthopedic disorders such as cruciate ligament disease. Also some evidence suggests that there is a correlation between increased time for growth plate closure and incidence of Hip Dysplasia (Todhunter et al. J. Am Vet. Assoc., 1997).
1. “Castration has no beneficial effect in dogs; however, lack of decrease in prostatic size after castration may help differentiate neoplasia from other prostatic diseases.” — Barsanti JA. Diseases of the prostate gland. in: Morgan RV, Bright RM, Swartout MS (Eds) Handbook of small animal practice, 4th edition, 2003.
2. “Castration of dogs with prostatic carcinoma can result in involution of the non-neoplastic portion of the prostate but does not alter the progression of the tumour.” — McEntee MC. Reproductive oncology. Clinical techniques in small animal practice 2002;17(3):133-149
3. Teske E, Naan EC, van Dijk EM, Van Garderen E, Schalken JA. Canine prostatic carcinoma: epidemiological evidence of an increased risk in castrated dogs. Molecular Cell Endocrinol 2002;197:251-255.
4. Ettinger SJ & Feldman EC (Eds) Textbook of veterinary internal medicine: diseases of the dog and cat, 5th edition, 2000.
5. Bell FW, Klausner JS, Hayden DW, Feeney DA, Johnston SD. Clinical and pathologic features of prostatic adenocarcinoma in sexually intact and castrated dogs: 31 cases (1970-1987). JAVMA 1991;199(11):1623-1630.
6. Waters DJ, Patronek GJ, Bostwick DG, Glickamn LT. Comparing the age at prostate cancer diagnosis in humans and dogs. J Natl Cancer Inst 1996;88(22):1686-1687.
7. Thrall MA, Olson PN, Freemeyer FG. Cytologic diagnosis of canine prostatic disease. J Am Anim Hosp Assoc 1985;21:95-102.<