Should you spay or neuter your dog – or not?

Standard spay and neuter surgery can have negative impacts on a dog’s health. So what are some alternative options?

In the US and Canada, broad scale sterilization has long been promoted as the best way to decrease dog overpopulation and euthanasia rates at shelters. This practice has become standard, with shelter dogs being sterilized before adoption, and most people spaying or neutering their dogs even if not adopted from a shelter. The decrease in the number of dogs entering shelters (currently six to eight million, down from 13 million in 1973), along with the resulting decrease in euthanasia rates, are cited as successful outcomes of spay/neuter programs. However, removing a dog’s reproductive organs can have adverse effects as well as benefits. This article looks at some alternatives to spay and neuter surgery.

Pros and cons of gonadectomy

Sterilization involves removing the dog’s reproductive organs. These procedures eliminate the hormones produced by these organs.

While gonadectomy makes it impossible for the animal to reproduce, what other impacts does a lack of sex hormones have? Research first evaluated the difference between early and later gonadectomy, usually supporting the early sterilization practice of sheltered animals. More recently, the research has broadened to compare large numbers of gonadectomized dogs with intact dogs.

This area of study is relatively new, but it indicates that gonadectomy confers a mixture of benefits and adverse effects, depending on age, breed and sex.

Pros: Eliminating sex hormones reduces mammary, ovarian and testicular cancers, prostatitis, benign prostatic hyperplasia, prostatic cysts and squamous metaplasia of the prostate. These dogs also experience a lower incidence of infectious disease.

Cons: Gonadectomized dogs have a higher incidence of many conditions, including obesity, urinary incontinence and calculi, atopic dermatitis, autoimmune hemolytic anemia, hypoadrenocorticism, diabetes mellitus, hypothyroidism, inflammatory bowel disease, hip dysplasia, cranial cruciate ligament rupture, aggressive and fearful behavior, cognitive dysfunction syndrome, prostate adenocarcinoma and transitional cell adenocarcinoma. Musculoskeletal issues may be especially significant for large breed dogs gonadectomized before they have finished growing, because bone physeal closure is delayed.

A significant contributor to the negative health impacts of gonadectomy is that the dog’s natural hormone feedback mechanisms become unregulated. Normally, the pituitary gland releases luteinizing hormone (LH), which then stimulates the production of steroid hormones from the gonads. Without the gonads, there is no feedback signal to reduce production, so LH concentrations remain very high for the remainder of the dog’s life. Receptors for LH are present in the urinary tract, skin, thyroid, blood vessels, ligaments, bone, synovium, immune cells and brain, thereby predisposing gonadectomized dogs to developing the health problems listed above.

Alternatives to traditional spay/neuter

1. Responsible pet ownership

While gonadectomy is viewed as the standard in the US, it is relatively uncommon in other regions of the world. In Norway and Sweden, for example, there are virtually no stray dogs and neutering is very uncommon, usually only allowable due to health concerns.

To avoid unwanted pregnancies, people with intact dogs must take special precautions. Females go into heat for a few days once or twice a year and need to be confined in an area without access to intact males. Male dogs should not be allowed to roam freely, as they are incredibly persistent in reaching a female in heat.

Other issues to consider include females bleeding while in heat; behavior changes that may be triggered by changing hormones; the logistics of having both male and female intact dogs in the same house; and health monitoring for diseases of the reproductive organs. Responsible dog owners are expected to manage these issues.

2. Hormone-sparing sterilization

Not everyone is prepared to keep their dogs intact while guaranteeing no unwanted pregnancies will occur. Luckily, there are options to ensure a dog is incapable of reproducing, while keeping his/her natural gonadal hormones to protect health.

Females: A hormone-sparing option that sterilizes a female dog involves conducting a hysterectomy (also called ovary-sparing spay or partial spay) by removing the uterus and leaving the ovaries intact.

After the procedure, the female dog is sterile and bleeding is eliminated. The female will still go into heat due to the influence of hormones produced by her ovaries, possibly showing behavioral changes around this time.

Ovarian cancer is often cited as an argument for removing ovaries — but ovarian cancer is rare, and the small risk does not outweigh the health benefits of preserving hormones. However, the dog should be monitored for mammary tumors after middle age. You can do this when you rub your dog’s tummy. These tumors are usually benign but should be removed promptly.

Males: A vasectomy sterilizes while sparing testosterone. The procedure involves severing or ligating the vas deferens, the duct that transports sperm. The procedure is quick and less invasive than castration.

Leaving the testicles and hormones intact does mean that testicular cancer, perianal gland tumors, and enlarged prostate may occur — but if they arise later in life, they are typically treated via castration. In such a case, the dog’s health still benefitted from years of natural hormones prior to castration. Also, prostate enlargement can be treated non-invasively with finasteride or by using pulsed electromagnetic therapy. Hormones will also influence the male dog’s behavior and interest in females in heat (see sidebar at right).

Moving forward

As our understanding grows around the long-term health consequences of gonadectomy in dogs, the demand for alternative options increases. Unfortunately, the supply of practitioners experienced in alternatives has not met the demand. In most veterinary schools in the US, students are not taught how to do hysterectomy or vasectomy, and the number of veterinarians offering these options is small.

However, Parsemus Foundation is doing its part to encourage education, dialog and communication with dog owners and practitioners. Their website ( offers information on hormone-sparing options, including extensive online training material for veterinarians on ovary-sparing spay. They also maintain a list of veterinarians who offer alternatives to traditional spay/neuter. Parsemus Foundation envisions a win-win future, when veterinarians offering choices are sought out by those who want the most appropriate methods of sterilization for their dogs.


The authors thank Elaine Lissner, founder and trustee of Parsemus Foundation, for her review of an earlier version of this article, and advocacy for innovative and alternative methods of pet sterilization.

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Dr. Linda Brent is a scientist and organizational leader with expertise in non-human primate behavior, animal welfare, non-profit management, project management, preclinical research, grant writing and scientific writing. She is a founder of Chimp Haven, Inc. — a sanctuary for chimpanzees retired from medical research — and served as its President and Director from 2002 to 2012. Dr. Brent is Executive Director for Parsemus Foundation, which funds innovative and neglected medical advancements.
Veterinarian Dr. Michelle Kutzler graduated from Washington State University College of Veterinary Medicine in 1993. She began a residency in veterinary reproduction at Cornell University in 1997 and became board-certified in Theriogenology in 1999. She earned a PhD in Physiology at Cornell University in 2002. Dr. Kutzler is an Associate Professor of Companion Animal Industries at Oregon State University.