Proper identification of dogs who have received hormone-sparing sterilization is critical to avoiding unnecessary repeat surgeries. Find out what you need to know about identifying dogs that have received a hysterectomy or vasctomy by applying a simple tattoo.
Use our Veterinarian Directory to find a veterinarian near you who offers hormone-sparing sterilization.
Hormone-sparing sterilization methods ensure population control while guarding the lifetime well-being of dogs. Hysterectomy (also called ovary-sparing spay) for females and vasectomy for males are ways to sterilize pets without the negative impacts from hormone loss. For a recent overview on the health implications of traditional spay and neuter, and a review of hormone-preserving contraceptive options, see this article in the Innovative Veterinary Care journal.
Pet owners can find veterinarians in your area offering ovary-sparing spay as an option. Veterinarians can review information on canine hysterectomy and vasectomy and register their veterinary clinic in the free directory to connect with clients. Also, visit the Facebook Ovary Sparing Spay and Vasectomy Group for a list of veterinarians who offer alternatives to traditional spay and neuter and to share your experiences.
Knowing whether a dog was sterilized is critical for preventing unnecessary repeat surgeries. However, lack of standardization has been a barrier. After a review of common identification methods for owned dogs and methods being used currently by veterinarians, a simple tattoo in the inguinal area is recommended as the standard for hormone-preserving sterilization methods:
Hysterectomy: Green “X” slightly lateral to midline near umbilicus
Vasectomy: Green “V” lateral and cranial to scrotal region
The simplicity of the marks does not require dedicated tattoo equipment or special skill, so that most veterinarians could provide the identification. Tattoos can be created using a needle or scalpel to apply the tattoo ink to the dermis. This video illustrates the technique. The procedure is completed while the dog is sedated for a sterilization procedure and no additional equipment is needed for detection. Although clarity of a tattoo may decrease over time, in this case it is not necessary that it is legible — just that it’s visible.
Looking for a veterinarian willing to perform procedures beyond surgical spay or neuter? Browse our directory of qualified veterinary professionals.
Do you offer alternative methods of contraception like ovary-sparing spay and vasectomy? Join our referral directory so new clients can find you.
See our searchable bibliography for a complete library of scientific publications on our projects.
Key publications on identification of dogs receiving HSS:
A: For decades, removing the gonads (ovaries/testes) was the standard for population control. However, research shows that these organs do more than just reproduce; they produce hormones (estrogen, progesterone, and testosterone) that are essential for development, bone density, muscle mass, and immune function. Removing them—especially in young dogs—can increase the risk of hip dysplasia, cruciate ligament tears, obesity, urinary incontinence, diabetes, and certain cancers like osteosarcoma or hemangiosarcoma.
A: Deciding to remove a dog’s reproductive organs is a trade-off. It effectively sterilizes the dog, but while it eliminates certain risks, it increases others.
A: Research indicates that when a dog is deprived of sex hormones during development or throughout adulthood, the following conditions are more frequently observed:
A: Without the sex hormones produced by the ovaries and testicles, the entire system becomes unbalanced. Normally, the hypothalamus and pituitary glands in the brain stimulate the production of luteinizing hormone (LH) and follicle stimulating hormone (FSH). The LH surge then stimulates the production of steroid hormones (like estrogen, progesterone or testosterone) from the gonads. Without the ovaries or testes, there is no feedback signal to the brain to reduce production, so LH continues to be over-produced. Diverse health problems likely result from the loss of sex hormones and the high LH levels.
A: No. Many owners worry that the only way to keep their dog healthy is to leave them fully intact, which carries the risk of accidental litters. Hormone-sparing sterilization (such as vasectomy or ovary-sparing spay/hysterectomy) offers a “middle ground.” These procedures make the dog 100% sterile (unable to reproduce) while allowing them to keep their natural hormones and the health protections they provide.
A: There is no single “correct” age for all dogs. The ideal timing depends heavily on the dog’s breed, sex, and lifestyle. For example, a Great Dane may need to remain intact longer to allow their joints to fully develop, whereas a small breed may have fewer risks associated with early sterilization. This is why an individualized approach is essential.
A: Yes, significantly. A landmark study of 35 different breeds showed that the “safe” age for sterilization varies wildly. For some breeds, neutering before one year of age significantly increases cancer and joint risks, while for others, the impact is minimal. Owners should consult breed-specific data before making a decision.
A: It is important to seek veterinary guidance from a professional who stays current on the latest research. You might ask: “Given my dog’s breed and health history, what are the specific risks of a traditional spay/neuter?” or “Are you familiar with hormone-sparing options like an Ovary-Sparing Spay or Vasectomy?” If your regular vet is not comfortable with these procedures, you can use the Parsemus Veterinary Directory to find a specialist who is.
A: This study indicated the longer the dog had natural hormones, the more improved their health and behavior were. This applied to dogs that were left intact longer, dogs that had an ovary-sparing spay, and dogs that had a vasectomy.
A: Similar to the procedure in humans, a canine vasectomy cuts or blocks the vas deferens – the tube that carries sperm from the testicles out of the body. This makes the dog sterile (unable to reproduce) but allows him to keep his testicles and his natural testosterone. He will still be interested in “intact” females, but he cannot father puppies.
A: In an OSS, the surgeon removes the uterus and part of the cervix but leaves one or both ovaries intact. This prevents pregnancy and eliminates the risk of “pyometra” (a life-threatening uterine infection), but the dog continues to produce the hormones necessary for healthy aging.
A: Yes. Because the ovaries remain, the dog will still experience hormonal cycles. She may attract males and exhibit some behavioral changes associated with heat, but because the uterus is gone, she will not have a bloody discharge and cannot become pregnant.
A: Hysterectomy or vasectomy will not change your dog’s behavior like traditional spaying and neutering. Because the dogs retain natural hormones, females will have a “dry” heat cycle and males may be interested in females in heat (although they cannot reproduce).
A: Yes. Most veterinary schools still only teach the traditional spay/neuter procedure. However, the Parsemus Foundation maintains a searchable directory of veterinarians who are trained and willing to perform hormone-sparing procedures.
A: It can be. Because it is a specialized procedure that requires more precision (to ensure all uterine tissue is removed while keeping ovaries safe), it may cost more than a high-volume, traditional spay. However, many owners view it as an investment in preventing future health costs and suffering.
A: Ovary-sparing spay in cats is uncommon due to limited research on health impacts of gonadectomy in cats and intolerance towards behaviors associated with cat hormones (spraying, fighting, howling in heat). However, many veterinarians in our Veterinary Directory provide ovary-sparing spay in at least dogs so feel free to contact those veterinarians and inquire about ovary-sparing spay for your cat.
A: The Parsemus Foundation’s Veterinary Directory lists specialists worldwide that can provide ovary-sparing spay procedures. In addition, you can discuss ovary-sparing spay with your regular veterinarian and share our page on Hormone-Sparing Sterilization Procedures with them. If you don’t find a veterinarian in your area, you may be able to find one by visiting the Ovary Sparing Spay and Vasectomy Info group on Facebook.
A: If a dog with a hormone-sparing procedure ends up in a shelter, a vet might assume they are completely intact and perform a second, unnecessary surgery. Clear identification prevents “re-spaying” or “re-neutering” and ensures the dog’s unique hormonal status is understood by future medical providers.
A: This is a major concern for owners of dogs with vasectomies or ovary-sparing spays. To an outside observer or a shelter, these dogs look “intact.” The Parsemus Foundation advocates for clear identification methods, such as a standardized tattoo on the abdomen (a small green “X” for hysterectomy or “V” for vasectomy). Adding specific notes in the dog’s microchip record will also be useful.
Last updated on September 10, 2026
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This website is educational and does not constitute medical advice or professional services. Those seeking personal medical advice should consult with a licensed physician.
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We occasionally share news about overlooked innovations in human and pet healthcare. Sign up to receive our human health and/or pet health e-newsletter.
We take your privacy seriously and will never share your contact information. See our Privacy Policy here.
The Parsemus Foundation is a private nonprofit operating foundation working to create meaningful improvements in human and pet health and welfare by advancing innovative and neglected medical research. Our aim is to educate medical professionals and the public about the latest developments in health and medicine.
You can email us at
info@parsemus.org
Our Professional Profile
can be found on ProPublica.
Write to Us
Parsemus Foundation,
2261 Market Street #24,
San Francisco, CA 94114
This website is educational and does not constitute medical advice or professional services. Those seeking personal medical advice should consult with a licensed physician.
