Neutering, from the Latin neŭter (of neither type), is the removal of an animal's reproductive organ, either all of it or a considerably large part of it. It is the most drastic surgical procedure with sterilizing purposes. The process in males is also referred to as castration, or gelding; while the process in females is also called spaying.

Unlike in humans, neutering is the most common sterilizing method in animals. While many agree on the advantages of neutering as a method of birth control, the necessity and humanity of this method (as opposed to alternative methods of birth control) and the political agendas within the debate are a subject of some controversy.

Household petsEdit

Most humane societies, animal shelters, and rescue groups (not to mention numerous commercial entities) urge pet owners to have their pets "spayed or neutered" to prevent the births of unwanted litters, contributing to the overpopulation of animals.

Additionally to being a birth control method, neutering has health benefits. Uterine, ovarian, and testicular cancer are prevented (although these cancers are not common in household animals), and hormone-driven diseases such as benign prostatic hypertrophy become a non-issue as well. Female cats and dogs are seven times more likely to develop mammary tumors if they are not spayed before their first heat cycle. [1] Unspayed dogs have a 25% chance of developing mammary tumors, about 50% of which are malignant. A dangerous common uterine infection known as pyometra is also prevented. Immediate complications of neutering include anesthetic and surgical complications. In the long run, dogs of both genders have an increased risk of obesity due to the fact that pet owners continue to feed as if the animal was still intact; this can be easily prevented by modifying the diet. Spayed female dogs sometimes develop urinary incontinence, and castrated males display a somewhat increased incidence of prostate cancer over intact males.[2] Neutered dogs have also been known to develop hormone-responsive alopecia (hair loss).[3] However, contrary to popular belief, neutered male cats are not more prone to urethral blockages than intact toms. A male cat's naturally longer, narrower urethra predispositions the animal for blockage whether it is neutered or not. Key factors in prevention include an increased fluid intake and a nutritious, minimally processed diet.[4] The procedures may also help to address behavioral issues that might otherwise result in animals being given up to shelters, abandoned, or euthanised. Obviously, the animals lose their libido, and females no longer experience heat cycles, which may be a major nuisance factor, especially in female cats. This is due to the hormonal changes involved with both genders. Minor personality changes may occur in the animal. Neutering is often recommended in cases of undesirable behavior in dogs, although studies suggest that while roaming, urine marking, and mounting are reduced in neutered males, it has little effect on aggression and other important behavioral issues. Intact male cats are more prone to urine spraying, while many common behavioral causes of urine marking remain in castrated cats.


Females (spaying)Edit

In female animals, spaying involves abdominal surgery to remove the ovaries and uterus (ovariohysterectomy). It is commonly practiced on household pets such as cats and dogs as a method of birth control, but is rarely performed on livestock.

The surgery is usually performed through a ventral (belly) midline incision below the umbilicus (belly button). The incision size varies depending upon the surgeon and the size of the animal. The uterine horns are identified and the ovaries are found by following the horns to their ends. There is a ligament that attaches the ovaries to the kidneys which needs to be broken so the ovaries can be identified. The ovarian arteries are then ligated twice (tied-off) with absorbable suture material and then the arteries transected (cut). The uterine body (which is very short in litter bearing species) and related arteries are also tied off just in front of the cervix (leaving the cervix as a natural barrier). The entire uterus and ovaries are then removed. The abdomen is checked for bleeding and then closed with a 3 layer closure. The linea alba (muscle layer) and then the subcutaneous layer (fat under skin) are closed with absorbable suture material. The skin is then stapled, sutured, or glued closed.

Males (castration)Edit

In male animals, castration involves the removal of the testes, and is commonly practiced on both household pets (for birth control) and on livestock (for birth control, as well as to improve commercial value).

Certain animals, like horses and swine, are usually treated with a scrotal castration (which can be done with the animal standing), while others, like dogs and cats, with a pre-scrotal castration (with the animal recumbent).

Methods of veterinary castration include surgical removal, the use of an elastrator tool to secure a band around the testicles that disrupts the blood supply, the use of a Burdizzo tool or emasculators to crush the spermatic cords and disrupt the blood supply, pharmacological injections and implants and immunological techniques to inoculate the animal against its own sexual hormones.

In veterinary practice an "open" castration refers to a castration in which the inguinal tunic is incised and not sutured. A "closed" castration refers to when the procedure is performed so that the inguinal tunic is sutured together after incision.

Modern nonsurgical alternativesEdit


  • Male dogs - Neutersol (Zinc gluconate neutralized by arginine).
  • Female mammals - Vaccine with Zona Pellucida antigens encapsulated in liposomes and an adjuvant, latest US patent RE37,224 (as of June 2006). Product commercially known as SpayVac[5], it causes a treated female mammal to produce antibodies that adhere to the surface of her ovum, blocking sperms from fertilizing it for a period of 22 months or more (depending on the animal).


  • Noninvasive vasectomy using ultrasound.[6]

Other issues surrounding the debateEdit

The spay and neuter debateEdit

The spay and neuter debate is an emotive and complex one. This section attempts to cover some of the background and main directions it has traveled. It is perhaps best considered under two broad aspects - the debate over animal sterilization, and the more specific debate that, if sterilization is appropriate, is spay and neuter (S&N) the right way to achieve it.

The main reason for advocation of general animal sterilization is that a large number of owners of animals are irresponsible, or that animals despite good care may breed without human approval. There are an immense number of unwanted and uncared for animals, and thousands are destroyed. So advocates strongly feel that animals (other than those actually intended to be responsibly bred) should be neutered, since owners often cannot or will not act responsibly if not, often with tragic animal consequences.

It is also a favored treatment to cure animal behavioral patterns that are sexually mediated, such as territorial marking, aggression, or sexual acts and solicitation, which embarrass and are unwanted by some owners. Spay and neuter succeeds in this because it removes the gross organs producing the relevant hormones.

A significant number of animal owners and those interested in animal welfare, whilst agreeing that there is much irresponsible breeding, do not agree that spay and neuter is the most appropriate approach to that problem. Reasons include that

A final reason is that certain clinical conditions are made more or less likely by the presence of hormones in the body. Both sides observe that some conditions are more common, some less so, if these organs are removed. Animal owners against spay and neuter argue that these hormones and organs have multiple and complex effects which are still not fully understood, and that people do not as a rule castrate other people to prevent illness. Instead we treat illnesses as and when they arise.

Other questions raised in the course of the debate include fro example:

  • Are desexed animals robbed of part of life? or given more life?
  • Does desexing make an animal safer?
  • Does desexing encourage a view that animals are commodities (modify as wished) and hence encourage abuse by removing aspects of animal behavior that people would otherwise have to acknowledge, and allowing idealization?
  • Animal sexuality -- should flawed *owner* irresponsibility be recognized by removal of major organs in *animals*?


  1. Morrison, Wallace B. (1998). Cancer in Dogs and Cats (1st ed.). Williams and Wilkins. ISBN 0-683-06105-4.
  2. Current Information on Prostate Disease, Testicular Neoplasia, and Undesirable Behavior in Male Dogs. URL accessed on May 14, 2005.
  3. Ettinger, Stephen J.;Feldman, Edward C. (1995). Textbook of Veterinary Internal Medicine(4th ed.). W.B. Saunders Company. ISBN 0-7216-6795-3.
  4. Urethral Obstruction and FLUTD in a Cat..
  5. SpayVac. Retrieved on early 2003.
  6. Fried NM, Sinelnikov YD, Pant BB, Roberts WW, Solomon SB (December 2001). "Noninvasive vasectomy using a focused ultrasound clip: thermal measurements and simulations". Biomedical Engineering, IEEE Transactions on 48 (12): 1453-9. PMID 11759926.

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