Spay and Neuter References

Below you'll find a collection of human-animal bond and animal behavior resources.

If you'd like to suggest additional resources, please e-mail mm@mmilani.com.

The following informal list explores some of many facets of spay and neuter. The goal is not to support or denounce the procedures, but merely to help individuals make an informed choice regarding this aspect of the human-companion animal relationship. Additional references are welcomed.

• General Background Information
• Medical Studies
• Online Sources

General background information:

• Kass, Phillip. (2000) Understanding Animal Companion Surplus in the United States Relinguishment of Nonadoptables to Animal shelters for Euthanasia, Journal of Applied Animal Welfare Science. 4(4), pp 237-248.
• Niehoff, Debra. (1999) The Biology of Violence (New York: Free Press). The entire book provides as excellent overview of the highly complex relationship between physiology and behavior. Chapter Six, "Raving Hormones," specifically addresses those related to sex.
• Rollin, Bernard E. and Rollin, Michael D.H. (2001). Dogmatism and Catechisms—Ethics and Companion Animals, Anthozoos, Vol XIV, 1:4-11. Explores the ethics of what the authors refer to as "gonad harvesting" in dogs and cats.

Historic background information:

• Kuefler, Matthew. (2001) The Manly Eunuch: Masculinity, Gender Ambiguity, and Christian Ideology in Late Antiquity. Chicago:Chicago Series on Sexuality, History, and Society. 245-282.
• Taylor, Gary. (2000) Castration: An Abbreviated History of Western Manhood. London: Routledge.

Medical Studies:

Studies that link spaying to breast (mammary) cancer prevention include: :

• Overley, G, Shofer, FS, Goldschmidt, MH et al. (2005) Association between ovariohysterectomy and feline mammary carcinoma. Journal of Veterinary Internal Medicine 19 (4): 560-563.

  This retrospective study of 204 female cats with mammary carcinoma and 200 control cats with other diseases indicates that cats spayed before 6 months of age had a 91% reduction in risk for mammary cancer. That dropped to 86% if they were spayed between 6 and 12 months. Any decrease between then and 24 months was insignificant.

• Schneinder, R. (1970) Comparison of Age, Sex and Incidence Rates in Human and Canine Breast Cancer, Cancer, Vol. 26, pp 419-426.
• Schneinder, R., Dorn, CR, and Taylor, D (1969). Factors Influencing Canine Mammary Cancer Development and Post-Surgical Survival Rates, Journal of the National Institutes of Cancer, Vol. 45, pp1249-1251.

These studies challenge that conclusion:

• Sonnenscheim, E.G.; Glickman, L.T., McKee, LJ, Goldschmidt, MH (1987). Nutritional risk factors for spontaneous breast cancer in pet dogs. American Journal of Epidemiology. 126:4, 736.
• Sonnenscheim, E.G.; Glickman, L.T., Goldschmidt, MH, McKee, LJ. (1991). Body conformation, diet, and risk of breast cancer in pet dogs; a case-control study. American Journal of Epidemiology. 133:7, 694-703.

Other medical studies:

• Aaron A, Eggleton K, Power C, Holt PE. (1996) Urethral sphincter mechanism incompetence in male dogs: a retrospective analysis of 54 cases. Veterinary Record. 139:542-6.
• Canine ovariohysterectomy and orchiectomy increases the prevalence of ACL injury. (2004) Clinical Orthropedics Related Research. Dec; (429):301-5.
• Carter, Rene, and Colitz, Carmen, M.H. (2002) The causes, diagnosis, and treatment of canine keratoconjunctivitis sicca. Veterinary Medicine. September, 2002: 680-694.
• Cooley, Dawn M. et al. (2002) Endogenenous gonadal hormone exposure and bone sarcoma risk, Cancer Epidemiology Biomarkers and Prevention, Vol. 11, 1434-1440, November 2002.
• Gilsanz, V. et al (1988) Effect of sex hormones on bone density in rabbits. AJP-Endocrinology and Metabolism. 225:4, E416-E421.
• Grumbach MM. (2000) Estrogen, bone, growth and sex: a sea change in conventional wisdom. Journal of Pediatric Endocrinology and Metabolism Supplement. 13 6:1439-55.
• Howe LM, Slater MR, Boothe HW, Hobson HP, Holcom JL, Spann AC. (2001) Long-term outcome of gonadectomy performed at an early age or traditional age in dogs. Journal of the American Veterinary Medical Association. 218(2):217-21.
• Kim, NN et al. (2004) Effects of ovariectomy and steroid hormones on vaginal smooth muscle contractility. International Journal of Impotence Research. 16:1, 43-50.
• Meuten DJ. Tumors in Domestic Animals. 4th Edition. (2002) Iowa State Press, Ames, Iowa, p. 575.
• Obradovich J, Walshaw R, Goullaud E. (1987) The influence of castration on the development of prostatic carcinoma in the dog. 43 cases (1978-1985). Journal of Veterinary Internal Medicine. Oct-Dec;1(4):183-7.
• Panciera DL. (1994) Hypothyroidism in dogs: 66 cases (1987-1992). Journal of the American Veterinary Medical Association. 204:761-767.
• Passina MA. et al. (2006) Differential effects of Estradiol, Progesterone, and Testosterone on Vaginal Structural Integrity. Endocrinology. 147:1, 61-69.
• Rawlings, C. Barsanti, J. A., Mahaffey, M.B. (2001). Treating incontinence in spayed female dogs. Journal of the American Veterinary Medical Association. 219:770-775.
• Ru G, Terracini B, Glickman LT. (1998) Host-related risk factors for canine osteosarcoma. Veterinary Journal (London, England) 1998 Jul;156(1):31-9
• Salmeri KR, Bloomberg MS, Scruggs SL, Shille V. (1991) Gonadectomy in immature dogs: effects on skeletal, physical, and behavioral development. Journal of the American Veterinary Medical Association. 198:1193-1203
• Stocklin-Gautschi NM, Hassig M, Reichler IM, Hubler M, Arnold S. (2001) The relationship of urinary incontinence to early spaying in bitches. Journal of Reproduction and. Fertility. Supplement. 57:233-36.
• Slauterbeck JR, Pankratz K, Xu KT, Bozeman SC, Hardy DM. (2004) Canine ovariohysterectomy and orchiectomy increases the prevalence of ACL injury. Clinical Orthopaedics and Relatated Research. 2004 Dec;(429):301-5.
• Spain et al. JAVMA 2004;224:380-387) showed that dogs spayed or neutered before 5 1/2 months had a significantly higher incidence of hip dysplasia than dogs spayed or neutered after 5 1/2 months of age.
• Ware WA, Hopper DL. (1999) Cardiac tumors in dogs: 1982-1995. Journal of Veterinary Internal Medicine. Mar-Apr;13(2):95-103.

Studies of various behavioral problems as a function of reproductive status, among others:

• Guy, N.C, U.A. Luescher, S.E. Dohoo, E. Spangler, J.B. Miller, I.R. Dohoo, L.A. Bate. (2001) Risk factors for dog bites to owners in a general veterinary caseload. Applied Animal Behaviour Science 74:29-42.
• Hart, B.L. (1968) Role of prior experience in the effects of castration on sexual behavior in male dogs, Journal of Comparative Physiological Psychology 66:719-725.
• Hart, B.L. (2001) Effect of gonadectomy on subsequent development of age-related cognitive impairment in dogs, Journal of the American Veterinary Medical Association 219:51-56.
• Leuner, Benedetta and Shors, Tracey J. (2006) Learning during motherhood: A resistance to stress. Hormones and Behavior (50) 1, pp 38-51. Based on their data, these researchers suggest that the presence of offspring and the nurturing and care-giving activities that they elicit protect females from the adverse effect of stress on processes involved in learning and memory.
• Lindsey, Steven R. (2000). Handbook of Applied Dog Behavior and Training: Volume I, Adaptation and Learning. Ames, Iowa: Iowa State University Press. Page 186-7 discusses the studies related to prenatal hormonal influences and the effects of sterilization.
• New, John. C. (2000) Characteristics of Shelter-Relinquished Animals and Their Owners Compared with Animals and Their Owners in U.S. Pet-Owning Household. Journal of Applied Animal Welfare Science. 3 (3), pp 179-201.
• Patronek, Gary J., Larry T. Glickman and Michael R. Moyer. (1995). Population Dynamics and Risk of Euthanasia for Shelter Dogs. Anthrozoos. Vol. VIII, No.1:31-43.
• Sandstrom, Noah J., Kim, Ju H. and Wasserman, Molly A. (2006) Testosterone modulates performance on a spatial working memory task in male rats. Hormones and Behavior (50) 1, pp 18-26. This study demonstrated that castration did not impair short-term (10-minute) memory in rats trained to go through a maze, but did diminish long-term (60-minute) memory.

Online sources:

• Early Spay-Neuter Considerations for the Canine Athlete
  This is a comprehensive overview, complete with references, written by veterinary pathologist and canine sports maven, Chris Zink.
• Oncolink, the cancer link of the College of Veterinary Medicine, Texas A&M. www.cvm.tamu.edu/oncology/faq/questions/incide01.html
• U.S. Pharmacist, The New Science of Estrogen Receptors, U.S. Pharmacist Continuing Education, ACPE Program No. 430-000-99-004-H01. www.uspharmacist.com/NewLook/CE/er/lesson.htm
  An excellent overview of estrogen receptors.
• Veterinary Cancer Registry at www.vetcancerregistry.com
  Veterinarians submit data on confirmed cancer cases that you can access by species, breed, reproductive status among other parameters.
• www.grca.org/healthsurvey.pdf
  This is a extensive collection of data about the golden retriever breed, including lifespan and cause of death.
• www.akcchf.org/pdfs/whitepapers/Biennial_National_Parent_Club_Canine_Health_Conference.pdf
  These notes from the 2005 AKC Canine Health Foundation Biennial National Parent Club Canine Health Conference are as interesting for what isn't there as for what is. A lot about ways to treat the problems that increasingly plague purebred dogs, but nothing about the effects spay and neuter might have on individual animals as breeds.

©2001-2008 Myrna Milani, DVM
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