Neutering, from the
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
''neuter'' ('of neither sex'), is the removal of an animal's
reproductive organ, either all of it or a considerably large part. The male-specific term is castration, while spaying is usually reserved for female animals. Colloquially, both terms are often referred to as fixing. In male horses, castrating is referred to as ''
gelding
A gelding is a castrated male horse or other equine, such as a pony, donkey or a mule. Castration, as well as the elimination of hormonally driven behavior associated with a stallion, allows a male equine to be calmer and better-behaved, makin ...
''. An animal that has not been neutered is sometimes referred to as ''
entire
Entire may refer to:
* Entire function, a function that is holomorphic on the whole complex plane
* Entire (animal), an indication that an animal is not neutered
* Entire (botany)
This glossary of botanical terms is a list of definitions of ...
'' or ''intact''.
Neutering is the most common method for animal
sterilization.
Humane societies,
animal shelter
An animal shelter or pound is a place where stray, lost, abandoned or surrendered animals – mostly dogs and cats – are housed. The word "pound" has its origins in the animal pounds of agricultural communities, where stray livestock would ...
s, and
rescue group
An animal rescue group or animal rescue organization is a group dedicated to pet adoption. These groups take unwanted, abandoned, abused, or feral, stray pets and attempt to find suitable homes for them. Many rescue groups are created by and run ...
s urge pet owners to have their pets neutered to prevent the births of unwanted
litters
Litter consists of waste products that have been discarded incorrectly, without consent, at an unsuitable location. Litter can also be used as a verb; to litter means to drop and leave objects, often man-made, such as aluminum cans, paper cups ...
, which contribute to the
overpopulation of unwanted animals in the rescue system. Many countries require that all adopted cats and dogs be sterilized before going to their new homes.
Methods of sterilization
Females (spaying)
![Female dog spay incision](https://upload.wikimedia.org/wikipedia/commons/b/bd/Female_dog_spay_incision.jpg)
Spaying is the surgical removal of the ovaries and uterus in female animals. It is commonly performed as a method of birth control and
behavior modification
Behavior modification is an early approach that used respondent and operant conditioning to change behavior. Based on methodological behaviorism, overt behavior was modified with consequences, including positive and negative reinforcement conti ...
.
In non-human animals, the technical term is an ovo-
hysterectomy or ovariohysterectomy; while in humans, this is called a hystero-
oophorectomy
Oophorectomy (; from Greek , , 'egg-bearing' and , , 'a cutting out of'), historically also called ''ovariotomy'' is the surgical removal of an ovary or ovaries. The surgery is also called ovariectomy, but this term is mostly used in reference ...
. One form of spaying is to remove only the ovaries (oophorectomy or ovariectomy), which is mainly done in
cat
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
s and young
dog
The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...
s. Another, less commonly performed method is an "ovary-sparing spay" in which the uterus is removed but one (or both) ovaries are left. A complete ovariohysterectomy may involve removal of the ovaries, uterus,
oviduct
The oviduct in mammals, is the passageway from an ovary. In human females this is more usually known as the Fallopian tube or uterine tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, o ...
s, and
uterine horns
The uterine horns (cornua of uterus) are the points in the upper uterus where the fallopian tubes exit to meet the ovaries. They are one of the points of attachment for the round ligament of uterus (the other being the mons pubis). They also prov ...
.
![Cat spay scar](https://upload.wikimedia.org/wikipedia/commons/6/69/Cat_spay_scar.jpg)
The surgery can be performed using
a traditional open approach or by
laparoscopic "keyhole" surgery. Open surgery is more widely available, as laparoscopic surgical equipment costs are expensive. Traditional open surgery is usually performed through a ventral midline incision below the
umbilicus. 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 body wall, which may need to be broken down so the ovaries can be identified. The ovarian arteries are then ligated with resorbable
suture material
A surgical suture, also known as a stitch or stitches, is a medical device used to hold body tissues together and approximate wound edges after an injury or surgery. Application generally involves using a needle with an attached length of thre ...
and then the arteries transected. 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 three-layer closure. The
linea alba and then the subcutaneous layer are closed with resorbable suture material. The skin is then stapled, sutured, or glued closed. For suturing the feline linea alba, the most appropriate suture bite and stitch interval size was suggested to be 5 mm.
Laparoscopic surgery is performed using a camera and instruments placed through small incisions (ports) in the body wall. The patient is under anaesthesia and lying on the back. The incisions are between and the number varies according to the equipment and technique used. The surgeon watches on a screen during the operation. The first port is made just behind the umbilicus and the camera is inserted. The abdomen is inflated with carbon dioxide gas to create a space in which to operate. A second port is introduced a few centimeters in front of the navel and a long grasping instrument called a Babcock forceps is inserted. The surgeon finds the ovary with the instrument and uses it to suspend the ovary from a needle placed through the abdominal wall. This lifts the ovary and uterus safely away from other organs. The surgeon then removes the grasping instrument and replaces it with an instrument that cauterizes and cuts tissue. This instrument uses electricity to heat the blood vessels to seal them and to cut them. No sutures are placed inside. The ovary is separated from the uterus and round ligament. The cautery instrument is removed and replaced by the grasping instrument, which is used to pull the ovary out through the small abdominal incision (port). This is repeated on the other side and the small holes are closed with a few sutures. Another method uses ligatures and even the uterus is removed. In female dogs only removing the ovaries and not the uterus is not state of the art because this way the risk of
pyometra
Pyometra or pyometritis is a uterine infection. Though it is most commonly known as a disease of the unaltered female dog, it is also a notable human disease. It is also seen in female cattle, horses, goats, sheep, swine, cats, rabbits, hamsters, ...
persists.
The benefits of laparoscopic surgery are less pain, faster recovery, and smaller wounds to heal. A study has shown that patients are 70% more active in the first three days post-surgery compared to open surgery. The reason open surgery is more painful is that larger incisions are required, and the ovary needs to be pulled out of the body, which stretches and tears tissue in the abdomen (it is not uncommon for patients to react under anaesthesia by breathing faster at this point).
Spaying in female dogs removes the production of
progesterone
Progesterone (P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the m ...
, which is a natural calming
hormone
A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required ...
and a
serotonin
Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter. Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and vas ...
uplifter. Spaying may therefore escalate any observable aggressive behaviour, either to humans or other dogs.
The risk of infections, bleeding, ruptures, inflammation and reactions to the drugs given to the animal as part of the procedure are all possibilities that should be considered.
Males (castration)
![Neutering incision on a dog](https://upload.wikimedia.org/wikipedia/commons/1/15/Neutering_incision_on_a_dog.jpg)
In male animals,
castration
Castration is any action, surgical, chemical, or otherwise, by which an individual loses use of the testicles: the male gonad. Surgical castration is bilateral orchiectomy (excision of both testicles), while chemical castration uses pharma ...
involves the removal of the
testes
A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testoster ...
(testicles), and is commonly practiced on both household pets (for birth control and behaviour modification) and on livestock (for birth control, as well as to improve commercial value). Often the term ''neuter
ng' is used to specifically mean castration, e.g. in phrases like "spay and neuter".
Surgical alternatives (vasectomy, tubal ligation, "gomerization")
Vasectomy
Vasectomy, or vasoligation, is an elective surgical procedure for male sterilization or permanent contraception. During the procedure, the male vasa deferentia are cut and tied or sealed so as to prevent sperm from entering into the urethra and ...
: In a more delicate procedure than castration, the
vasa deferentia
The vas deferens or ductus deferens is part of the male reproductive system of many vertebrates. The ducts transport sperm from the epididymis to the ejaculatory ducts in anticipation of ejaculation. The vas deferens is a partially coiled tube ...
– ducts that run from the testes to the
penis
A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males do n ...
– are cut then tied or sealed, to prevent
sperm
Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, whi ...
from entering into the
urethra
The urethra (from Greek οὐρήθρα – ''ourḗthrā'') is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra con ...
. Failure rates are insignificantly small.
Breeders
A breeder is a person who selectively breeds carefully selected mates, normally of the same breed to sexually reproduce offspring with specific, consistently replicable qualities and characteristics. This might be as a farmer, agriculturalist, ...
routinely have this procedure carried out on male
ferret
The ferret (''Mustela furo'') is a small, Domestication, domesticated species belonging to the family Mustelidae. The ferret is most likely a domesticated form of the wild European polecat (''Mustela putorius''), evidenced by their Hybrid (biol ...
s and
sheep
Sheep or domestic sheep (''Ovis aries'') are domesticated, ruminant mammals typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus ''Ovis'', in everyday usage it almost always refers to domesticated s ...
to manipulate the estrus cycles of in-contact females. It is uncommon in other animal species. Because a vasectomy is usually a more expensive procedure, among pet-keepers it is more often performed on
show animals, to cosmetically preserve their appearance (though depending upon the
fancier organization, the procedure may invalidate the animal's candidacy for certain awards, or relegate it to a non-
pedigree, generic "household pet" competition division, just as with full castration).
Tubal ligation
Tubal ligation (commonly known as having one's "tubes tied") is a surgical procedure for female sterilization in which the fallopian tubes are permanently blocked, clipped or removed. This prevents the fertilization of eggs by sperm and thus th ...
: Snipping and tying of
fallopian tubes as a sterilization measure can be performed on female cats, dogs, and other species; it is essentially the female equivalent of vasectomy, but a more invasive procedure. Risk of unwanted pregnancies is insignificantly small. Only a few veterinarians perform the procedure.
Like other forms of neutering, vasectomy and tubal ligation eliminate the ability to produce offspring. They differ from neutering in that they leave the animal's levels and patterns of
sex hormone
Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormones that interact with vertebrate steroid hormone receptors. The sex hormones include the androgens, estrogens, and progestogens. Their effect ...
unchanged. Both sexes will retain their normal reproductive behavior, and other than birth control, none of the advantages and disadvantages listed above apply. This method is favored by some people who seek minimal infringement on the natural state of companion animals to achieve the desired reduction of unwanted births of cats and dogs.
"" is breeders' informal term for surgical techniques by which male livestock, such as bulls, retain their full
libido
Libido (; colloquial: sex drive) is a person's overall sexual drive or desire for sexual activity. Libido is influenced by biological, psychological, and social factors. Biologically, the sex hormones and associated neurotransmitters that act u ...
(and related effects like sex
pheromones
A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
that would be lost through castration), but are rendered incapable of
copulation
Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetra ...
. This is done to stimulate and identify
estrous
The estrous cycle (, originally ) is the set of recurring physiological changes that are induced by reproductive hormones in most mammalian therian females. Estrous cycles start after sexual maturity in females and are interrupted by anestrous p ...
females without the risk of transmitting
venereal diseases
Sexually transmitted infections (STIs), also referred to as sexually transmitted diseases (STDs) and the older term venereal diseases, are infections that are spread by sexual activity, especially vaginal intercourse, anal sex, and oral s ...
or causing a pregnancy by a male other than the one intended for
selective breeding
Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant m ...
. Animals altered for this purpose are referred to as teasers (teaser bulls, etc.), or gomers. Several methods are used. Penile translocation surgically alters the penis to point far enough away from its normal direction that it cannot manage
vagina
In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen ...
l penetration. Penile fixation permanently attaches the penis to the abdomen so that it cannot be lowered for penetration.
Penectomy
Penectomy is penis removal through surgery, generally for medical or personal reasons.
Medical reasons for penectomy
Cancer, for example, sometimes necessitates removal of part or all of the penis. The amount of penis removed depends on the se ...
is the partial or complete removal of the
penis
A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males do n ...
.
Nonsurgical alternatives
Injectable
* Male dogs – Two intratesticular injectable formulations are known to sterilize male dogs. Zeuterin was approved by the United States
Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
(FDA) for permanent sterilization of male dogs ages three months and older by causing
necrosis
Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
of the testicle. It is not currently available commercially. Calcium chloride dissolved in a variety of diluents have also been studied, with the majority of research and most promising results using calcium chloride dissolved in ethyl alcohol. Calcium chloride formulations can be purchased for use in animals from compounding pharmacies, but the use of calcium chloride for sterilization of males is not approved by the FDA or any other international regulatory agency.
* Male cats – Calcium chloride formulations have also been studied in male cats.
* Male rats –
Adjudin
Adjudin (AF-2364) is a drug which is under development as a potential non-hormonal male contraceptive drug, which acts by blocking the production of sperm in the testes, but without affecting testosterone production. It is an analogue of the ch ...
(
analogue of indazole-carboxylic acid), induces reversible germ cell loss from the
seminiferous epithelium by disrupting cell adhesion function between
nurse cells and
immature sperm cells, preventing
maturation.
* Male mice – injection of a solution of the JQ1 molecule to bind to a pocket of BRDT necessary for chromatin remodeling, which gives the proteins that regulate how genes act access to the genetic material
* Male sheep and pigs – Wireless Microvalve. A proposed non-chemical, reversible sterilization method using a
piezoelectric
Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied Stress (mechanics), mechanical s ...
polymer
A polymer (; Greek '' poly-'', "many" + ''-mer'', "part")
is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
that will deform when exposed to a specific electric field broadcast from an emitter. The valve will then open or close, preventing the passage of sperm, but not
seminal fluid
Semen, also known as seminal fluid, is an organic bodily fluid created to contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. Semen i ...
. Located in a section of the
vas deferens
The vas deferens or ductus deferens is part of the male reproductive system of many vertebrates. The ducts transport sperm from the epididymis to the ejaculatory ducts in anticipation of ejaculation. The vas deferens is a partially coiled tube ...
that occurs just after the
epididymis, the implantation can be carried out by use of a hypodermic needle.
* Female mammals – Vaccine of antigens (derived from purified
porcine zona pellucida Porcine zona pellucida (PZP) is the zona pellucida extracted from the ovaries of pigs which is used as a source of antigens for immunocontraception.
The zona pellucida is a thick membrane that surrounds the unfertilised eggs of mammals. In order fo ...
) encapsulated in liposomes (cholesterol and lecithin) with an adjuvant, latest US paten
RE37,224(as of 2006-06-06), CA paten
2137263(issued 1999-06-15). Product commercially known as SpayVac, a single injection causes a treated female mammal to produce antibodies that bind to
ZP3
Zona pellucida sperm-binding protein 3, also known as zona pellucida glycoprotein 3 (Zp-3) or the sperm receptor, is a ZP module-containing protein that in humans is encoded by the ''ZP3'' gene. ZP3 is the receptor in the zona pellucida which bin ...
on the surface of her ovum, blocking sperm from fertilizing it for periods from 22 months up to 7 years (depending on the animal). This will not prevent the animal from going into heat (ovulating) and other than birth control, none of the above-mentioned advantages or disadvantages apply.
Other
* Male mice – reversible regulation of the KATNAL1 gene in the Sertoli cell microtubule dynamics of the testes.
* Female mammals – orally administered phosphodiesterase 3 inhibitor ORG 9935 daily before and during ovulation, which blocks the resumption of meiosis resulting in ovulation of a non-fertilizable, immature oocyte without rupturing the follicle.
Early-age neutering
Early-age neutering, also known as
pediatric spaying or prepubertal gonadectomy, is the removal of the ovaries or testes before the onset of
puberty
Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a boy. ...
. It is used mainly in animal sheltering and rescue where puppies and kittens can be neutered before being adopted out, eliminating non-compliance with sterilization agreement, which is typically above 40%.
The
American Veterinary Medical Association
The American Veterinary Medical Association (AVMA), founded in 1863, is a not-for-profit association representing more than 99,500 veterinarians in the US.
The AVMA provides information resources, continuing education opportunities, publicatio ...
,
American Animal Hospital Association
The American Animal Hospital Association (AAHA) is a non-profit organization for companion animal veterinary hospitals. Established in 1933, the association is the only accrediting body for small animal hospitals in the U.S. and Canada. The ass ...
and the
Canadian Veterinary Medical Association
The Canadian Veterinary Medical Association (CVMA) (french: Association canadienne des médecins vétérinaires, ACMV), founded in 1876, provides leadership on national veterinary issues, advocates for animal welfare, and works to encourage life b ...
support the procedure for population control, provided that the veterinarian uses their best knowledge when making the decision about the age at neutering.
[Dog and Cat Spay/Castration](_blank)
at CanadianVeterinarians.net A task force recommends that cats are spayed–neutered prior to 5 months of age.
While the age-unrelated risks and benefits cited above also apply to early-age neutering, various studies have indicated that the procedure is safe and not associated with increased mortality or serious health and behavioral problems when compared to conventional age neutering.
Anesthesia recovery in young animals is usually more rapid and there are fewer complications.
One study found that in female dogs there is an increasing risk of urinary incontinence the earlier the procedure is carried out; the study recommended that female dogs be spayed no earlier than 3 to 4 months of age.
A later study comparing female dogs spayed between 4 and 6 months and after 6 months showed no increased risk.
One study showed the incidence of hip dysplasia increased to 6.7% for dogs neutered before 5.5 months compared to 4.7% for dogs neutered after 5.5 months, although the cases associated with early age neutering seems to be of a less severe form. There was no association between age of neutering and arthritis or long-bone fractures.
Another study showed no correlation between age of neutering and musculoskeletal problems.
A study of large breed dogs with
cranial cruciate ligament
The anterior cruciate ligament (ACL) is one of a pair of cruciate ligaments (the other being the posterior cruciate ligament) in the human knee. The two ligaments are also called "cruciform" ligaments, as they are arranged in a crossed formation. ...
rupture associated early-age neutering with the development of an excessive tibial plateau angle.
Of particular note are two recent studies from Lynette Hart's lab at UC Davis. The first study from 2013, published in a well-known interdisciplinary peer-reviewed journal demonstrated "no cases of CCL (cruciate ligament tear) diagnosed in intact males or females, but in early-neutered males and females the occurrences were 5 percent and 8 percent, respectively. Almost 10 percent of early-neutered males were diagnosed with LSA (lymphosarcoma), 3 times more than intact males. The percentage of HSA (hemangiosarcoma) cases in late-neutered females (about 8 percent) was 4 times more than intact and early-neutered females. There were no cases of MCT (mast cell tumor) in intact females, but the occurrence was nearly 6 percent in late-neutered females".
The second study from 2014 highlighted significant difference in closely related breeds (retrievers), suggesting that inter-breed variability is quite high and that sweeping legal measures and surgical mandates are not the best solutions to canine welfare and health. Specifically the study states: "In Labrador Retrievers, where about 5 percent of gonadally intact males and females had one or more joint disorders, neutering at 6 months doubled the incidence of one or more joint disorders in both sexes. In male and female Golden Retrievers, with the same 5 percent rate of joint disorders in intact dogs, neutering at 6 months increased the incidence of a joint disorder to 4–5 times that of intact dogs. The incidence of one or more cancers in female Labrador Retrievers increased slightly above the 3 percent level of intact females with neutering. In contrast, in female Golden Retrievers, with the same 3 percent rate of one or more cancers in intact females, neutering at all periods through 8 years of age increased the rate of at least one of the cancers by 3–4 times. In male Golden and Labrador Retrievers neutering had relatively minor effects in increasing the occurrence of cancers."
In terms of behavior in dogs, separation anxiety, aggression, escape behavior and inappropriate elimination are reduced while noise phobia and sexual behavior was increased. In males with aggression issues, earlier neutering may increase barking.
In cats,
asthma
Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
, gingivitis, and hyperactivity were decreased, while shyness was increased. In male cats, occurrence of abscesses, aggression toward veterinarians, sexual behaviors, and
urine spraying
Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...
was decreased, while hiding was increased.
Health and behavioral effects
Advantages
Besides being a birth control method, and being convenient to many owners, castrating/spaying has the following health benefits:
*
Sexually dimorphic
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
behaviors such as
mounting and
urine spraying
Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...
are reduced due to the decrease in hormone levels brought about by neutering. In species other than dogs, certain forms of male
aggression
Aggression is overt or covert, often harmful, social interaction with the intention of inflicting damage or other harm upon another individual; although it can be channeled into creative and practical outlets for some. It may occur either reacti ...
are also reduced. Sexual behavior in cats seems to make them especially undesirable to pet owners.
* Early spaying significantly reduces the risk of development of mammary tumours in female dogs. The incidence of mammary tumours in un-spayed female dogs is 71% (of which approximately 50% will be malignant and 50% will be benign), but if a dog is spayed before its first heat cycle, the risk of developing a mammary tumour is reduced to 0.35%—a 99.5% reduction. The positive effects of spaying on reduction of later mammary tumours decreases with each heat the dog has (backing up the contention that the greatest benefit to reduce future mammary tumour development is to spay before the first heat), and there is no added benefit to spaying to reduce recurrence of a mammary tumour once it has been diagnosed.
* Neutering increases life expectancy in cats: one study found castrated male cats live twice as long as intact males, while spayed female cats live 62% longer than intact females. Non-neutered cats in the U.S. are three times more likely to require treatment for an animal bite. Having a cat neutered confers health benefits, because castrated males cannot develop testicular cancer, spayed females cannot develop uterine, cervical or ovarian cancer, and both have a reduced risk of mammary cancer.
* Without the ability to reproduce, a female necessarily has zero risk of pregnancy complications, such as
spotting and
false pregnancy
False pregnancy (or pseudocyesis, from the Greek "false" and "pregnancy") is the appearance of clinical or subclinical signs and symptoms associated with pregnancy although the individual is not physically carrying a baby. The mistaken impressi ...
, the latter of which can occur in more than 50% of unspayed female dogs.
*
Pyometra
Pyometra or pyometritis is a uterine infection. Though it is most commonly known as a disease of the unaltered female dog, it is also a notable human disease. It is also seen in female cattle, horses, goats, sheep, swine, cats, rabbits, hamsters, ...
,
uterine cancer
Uterine cancer, also known as womb cancer, includes two types of cancer that develop from the tissues of the uterus. Endometrial cancer forms from the lining of the uterus, and uterine sarcoma forms from the muscles or support tissue of the uteru ...
,
ovarian cancer
Ovarian cancer is a cancerous tumor of an ovary. It may originate from the ovary itself or more commonly from communicating nearby structures such as fallopian tubes or the inner lining of the abdomen. The ovary is made up of three different c ...
, and
testicular cancer
Testicular cancer is cancer that develops in the testicles, a part of the male reproductive system. Symptoms may include a lump in the testicle, or swelling or pain in the scrotum. Treatment may result in infertility.
Risk factors include an ...
are prevented, as the susceptible organs are removed, though
stump pyometra may still occur in spayed females.
* Pyometra (or a pus filled womb) ('Pyo' = pus; 'metra' = uterus or womb) is a life-threatening condition that requires emergency veterinary treatment. The risk of a non-spayed female dog developing pyometra by age 10 is 25% across all breeds, but can be as high as 54% in some breeds. The treatment of choice for a closed-pyometra (where the cervix is closed and the pus cannot drain) is admission to hospital, commencement on intravenous fluids and appropriate antibiotics and, once stable enough for the anaesthetic and surgery, emergency removal of the infected pus-filled uterus. Medical management can be attempted if the animal's condition allows (for example in the case of an 'open' pyometra where the pus drains per-vaginum from the uterus via the open cervix) or dictates (where the animal is too old or otherwise unwell to withstand surgery), if the owner wishes to keep the dog entire to breed or if the owner is unable to afford the veterinary fees associated with surgery. Emergency removal of the infected uterus carries a much higher degree of risk of death than a routine 'spay' operation. The risk of death from in dogs undergoing surgical treatment for pyometra is up to 17%. Thus the risk of death in entire female dogs from a pyometra, even if given correct veterinary attention can be up to 9% by 10 years of age (17% of 54%). This risk is reduced to virtually zero if spayed.
Disadvantages
General
* As with any surgical procedure, immediate complications of neutering include the usual
anesthetic
An anesthetic (American English) or anaesthetic (British English; see spelling differences) is a drug used to induce anesthesia — in other words, to result in a temporary loss of sensation or awareness. They may be divided into two ...
and
surgical
Surgery ''cheirourgikē'' (composed of χείρ, "hand", and ἔργον, "work"), via la, chirurgiae, meaning "hand work". is a medical specialty that uses operative manual and instrumental techniques on a person to investigate or treat a pat ...
complications, such as bleeding, infection, and death. These risks are relatively low in routine neutering; however, they may be increased for some animals due to other pre-existing health factors. In one study the risk of anesthetic-related death (not limited to neutering procedures) was estimated at 0.05% for healthy dogs and 0.11% for healthy cats. The risks for sick animals were 1.33% for dogs and 1.40% for cats.
* Spaying and castrating cats and dogs may increase the risk of
obesity
Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's we ...
if nutritional intake is not reduced to reflect the lower metabolic requirements of neutered animals.
In cats, a decrease in sex hormone levels seems to be associated with an increase in food intake.
In dogs, the effects of neutering as a risk factor for obesity vary among breeds.
* Neutered dogs of both sexes are at a twofold excess risk to develop
osteosarcoma
An osteosarcoma (OS) or osteogenic sarcoma (OGS) (or simply bone cancer) is a cancerous tumor in a bone. Specifically, it is an aggressive malignant neoplasm that arises from primitive transformed cells of mesenchymal origin (and thus a sarcoma ...
(bone cancer) as compared to intact dogs. The risk of osteosarcoma increases with increasing breed size and especially height.
* Studies of cardiac tumors in dogs showed that there was a 5 times greater risk of
hemangiosarcoma
Hemangiosarcoma is a rapidly growing, highly invasive variety of cancer that occurs almost exclusively in dogs, and only rarely in cats, horses, mice, or humans (vinyl chloride toxicity). It is a sarcoma arising from the lining of blood vessels; ...
(cancer of blood vessel lining), one of the three most common cancers in dogs, in spayed females than intact females and a 2.4 times greater risk of hemangiosarcoma in castrated dogs as compared to intact males.
* Spaying and castrating is associated with an increase in urinary tract cancers in dogs, however the risk is still less than 1%.
* Neutered dogs of both sexes have a 27% to 38% increased risk of adverse reactions to vaccinations. However, the incidence of adverse reactions for neutered and intact dogs combined is only 0.32%.
* Neutered dogs have also been known to develop hormone-responsive
alopecia
Hair loss, also known as alopecia or baldness, refers to a loss of hair from part of the head or body. Typically at least the head is involved. The severity of hair loss can vary from a small area to the entire body. Inflammation or scar ...
(hair loss).
* A 2004 study found that neutered dogs had a higher incidence of cranial cruciate ligament (CCL) rupture, a form of anterior cruciate ligament (ACL) injury.
* A study of
golden retrievers
The Golden Retriever is a Scottish breed of retriever dog of medium size. It is characterised by a gentle and affectionate nature and a striking golden coat. It is commonly kept as a pet and is among the most frequently registered breeds ...
found that castrated males were 3 times more likely than intact males to be diagnosed with
lymphoma
Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enlar ...
and 2 times more likely to have
hip dysplasia
Hip dysplasia is an abnormality of the hip joint where the socket portion does not fully cover the ball portion, resulting in an increased risk for joint dislocation. Hip dysplasia may occur at birth or develop in early life. Regardless, it doe ...
.
* Castration and spaying can also increase the risk of geriatric cognitive impairment, as noted in Laura J. Sanborn's meta-analysis.
* About 2% of castrated
male dogs eventually develop
prostate cancer
Prostate cancer is cancer of the prostate. Prostate cancer is the second most common cancerous tumor worldwide and is the fifth leading cause of cancer-related mortality among men. The prostate is a gland in the male reproductive system that sur ...
, compared to less than 0.6% of intact males.
The evidence is most conclusive for
Bouviers.
[
* In a study of 29 intact male dogs and 47 castrated males aged 11–14, the neutered males were significantly more likely to progress from one geriatric cognitive impairment condition (out of the four conditions – disorientation in the house or outdoors, changes in social interactions with human family members, loss of house training, and changes in the sleep-wake cycle) to two or more conditions. Testosterone in intact males is thought to slow the progression of cognitive impairment, at least in dogs that already have mild impairment.
* As compared to intact males, castrated cats are at an increased risk for certain problems associated with ]feline lower urinary tract disease
Feline lower urinary tract disease (FLUTD) is a generic category term to describe any disorder affecting the bladder or urethra of cats.
It encompasses around 10 different diseases of the lower urinary tract, all of which can present with very si ...
. They are much more likely to suffer from feline cystitis
Feline idiopathic cystitis (FIC) or feline interstitial cystitis or cystitis in cats, is one of the most frequently observed forms of feline lower urinary tract disease (FLUTD). Feline cystitis means "inflammation of the bladder in cats". The te ...
which can escalate into a life-threatening urethral blockage.
* Neutering also has been associated with an increased likelihood of urethral sphincter incontinence in male dogs.
* There is evidence that spaying can increase the risk of urinary incontinence
Urinary incontinence (UI), also known as involuntary urination, is any uncontrolled leakage of urine. It is a common and distressing problem, which may have a large impact on quality of life. It has been identified as an important issue in geria ...
in dogs, especially when done before the age of three months. Up until 12 months of age, the risk decreases as the age at spaying increases. Urinary incontinence can affect up to one out of five spayed female dogs, and develops an average of 2.9 years after the dog has been spayed.
* Spayed female dogs are at an increased risk of hypothyroidism.
Current research
Various studies of the effects neutering has overall on male and female dog aggression have been unable to arrive at a consensus. A possible reason for this according to two studies is changes to other factors have more of an effect than neutering. One study reported results of aggression towards familiar and strange people and other dogs reduced between 10 and 60 percent of cases, while other studies reported increases in possessive aggression and aggression towards familiar and strange people, and more studies reported there was no significant difference in aggression risk between neutered and non-neutered males. For females with existing aggression, many studies reported increases in aggressive behavior and some found increased separation anxiety behavior. A report from the American Kennel Club Canine Health Foundation reported significantly more behavioral problems in castrated dogs. The most commonly observed behavioral problem in spayed females was fearful behavior and the most common problem in males was aggression. Early age gonadectomy is associated with an increased incidence of noise phobias and .
Terminology for neutered animals
A specialized vocabulary is used in animal husbandry
Animal husbandry is the branch of agriculture concerned with animals that are raised for meat, fibre, milk, or other products. It includes day-to-day care, selective breeding, and the raising of livestock. Husbandry has a long history, starti ...
and animal fancy
Animal fancy is a hobby involving the appreciation, promotion, or breeding of pet or domestic animals.
Fancy may include ownership, showing, animal sports and other competitions, and breeding. Hobbyists may simply collect specimens of the animal ...
for neutered (castrated) animals:
Religious views
Islam
There are differing views in Islam
Islam (; ar, ۘالِإسلَام, , ) is an Abrahamic religions, Abrahamic Monotheism#Islam, monotheistic religion centred primarily around the Quran, a religious text considered by Muslims to be the direct word of God in Islam, God (or ...
with regard to neutering animals, with some Islamic associations stating that when done to maintain the health and welfare of both the animals and the community, neutering is allowed on the basis of being in the interest of 'maslaha
Maslaha or maslahah ( ar, مصلحة, lit=public interest) is a concept in shari'ah ( Islamic divine law) regarded as a basis of law.I. Doi, Abdul Rahman. (1995). "Mașlahah". In John L. Esposito. ''The Oxford Encyclopedia of the Modern Islamic Wo ...
' (general good) or "choosing the lesser of two evils".
Judaism
Orthodox Judaism
Orthodox Judaism is the collective term for the traditionalist and theologically conservative branches of contemporary Judaism. Theologically, it is chiefly defined by regarding the Torah, both Written and Oral, as revealed by God to Moses on M ...
forbids the castration of both humans and non-human animals by Jews, except in lifesaving situations. In 2007, the Sephardic
Sephardic (or Sephardi) Jews (, ; lad, Djudíos Sefardíes), also ''Sepharadim'' , Modern Hebrew: ''Sfaradim'', Tiberian Hebrew, Tiberian: Səp̄āraddîm, also , ''Ye'hude Sepharad'', lit. "The Jews of Spain", es, Judíos sefardíes (or ), ...
Chief Rabbi
Chief Rabbi ( he, רב ראשי ''Rav Rashi'') is a title given in several countries to the recognized religious leader of that country's Jewish community, or to a rabbinic leader appointed by the local secular authorities. Since 1911, through a ...
of Israel
Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...
Rabbi Shlomo Amar
Shlomo Moshe Amar ( he, שלמה משה עמאר; ar, سليمان موسى عمار; born April 1, 1948)Gantz, Nesanel. "A Chief Rabbi of the Past and Future". '' Ami'', November 5, 2014, pp. 26-27. is the former Sephardic Chief Rabbi of Isra ...
issued a ruling stating that it is permissible to have companion animals neutered on the basis of the Jewish mandate to prevent cruelty to animals.
See also
* Animal population control
Population control is the practice of artificially maintaining the size of any population. It simply refers to the act of limiting the size of an animal population so that it remains manageable, as opposed to the act of protecting a species from ...
* Animal shelter
An animal shelter or pound is a place where stray, lost, abandoned or surrendered animals – mostly dogs and cats – are housed. The word "pound" has its origins in the animal pounds of agricultural communities, where stray livestock would ...
* Cruelty to animals
* Hysterectomy
* Oophorectomy
Oophorectomy (; from Greek , , 'egg-bearing' and , , 'a cutting out of'), historically also called ''ovariotomy'' is the surgical removal of an ovary or ovaries. The surgery is also called ovariectomy, but this term is mostly used in reference to ...
* Overpopulation in companion animals In some countries there is an overpopulation of pets such as cats, dogs, and exotic animals. In the United States, six to eight million animals are brought to shelters each year, of which an estimated three to four million are subsequently euthani ...
* Wildlife contraceptive
Wildlife contraceptives are contraceptives used to regulate the fertility of wild animals. They are used to control population growth of certain wild animals.
Usage
White-tailed deer may be controlled with contraceptives in suburban areas, whe ...
* World Spay Day World Spay Day advocates spaying, or neutering, advocating it "as a proven means of saving the lives of companion animals, community (feral and stray) cats, and street dogs who might otherwise be put down in a shelter or killed on the street." It is ...
References
External links
{{wiktionary, spaying
DVM Article on health effects of spay/neuter: Long-Term Health Risks and Benefits Associated with Spay / Neuter in Dogs
Determining the optimal age for gonadectomy of dogs and cats, AVMA (pdf)
Canine Spay Photos and Description
Castration
Veterinary castration
Dog health
Surgical removal procedures
Cat health
Animal welfare