Copyright 1995 - 2010 Sarah Hartwell

The following was originally written in response to a letter which condemned the neutering of cats. It has been modified for use on this site. The author of the original letter claimed that:

- Neutering is nothing more than an attempt to denature cats
- Neutering is not in the best interests of cats and there is no over-population problem
- Non-neuterers provide a service to owners because shelters have a kitten shortage caused by their own excessive neutering
- Neutering will lead to the extinction of healthy (i.e. mixed-breed) cats
- Pro-neuterers do not care about cats
- All neutering, particularly early age neutering, is barbaric and neutered cats are unhealthy
- Allowing pet cats to breed freely is not irresponsible and does not contribute to over-population
- Cats should be allowed to roam freely, keeping cats indoors is cruel and an infringement of their rights to roam and reproduce

I wish to contest X’s views against neutering of cats, including early neutering. Cat rescue and welfare societies are constantly working to improve cat care and welfare and while I accept that X believes herself to be well-meaning, the views expressed rely more on emotion than on rational consideration of feline population. Such views do nothing to improve the lot of the cat and represent a step backwards in terms of feline welfare.

"Supporters of early neutering do not love kittens."

Supporters of early neutering love kittens as much as anyone, but they have also seen what happens to ‘surplus’ cats and kittens. Many are abandoned, left in boxes outside shelters/vet surgeries or simply thrown into dustbins. One of the least recognised cruelties to animals, and one perpetrated by well-intentioned but misguided individuals, is the continued breeding of kittens contributing to the ongoing problem of ‘surplus’ cats and kittens. Compliance rates with shelter policies of neutering at 5-6 months is believed to be only 50-60%. To prevent further overpopulation a higher compliance rate is needed; early neutering by shelters brings the compliance rate to 100%.

Early neutering of kittens is now moving from being a "controversial" issue to wider acceptance. In Australia and the US many people prefer to obtain their kittens already neutered. Aside from the behavioural aspects, there are sound, scientifically documented reasons to neuter cats. Spayed females are protected against mammary cancer and uterine infections. In males, castration reduces the risk of testicular cancer and enlargement of the prostate and related infections. From a behavioural standpoint, neutered animals are more reliable, stable and US suggest that neutered cats have about 60% less problems than those left "intact" as well as a life expectancy twice that of unneutered cats.

Studies into early neutering

Early spay/neuter (6 - 14 weeks of age) has been practised for over 25 years in North America and vets have followed the cats’ development. The concept of early neutering (before sexual maturity) is nothing new. In the early 1900's, early neutering was the norm. The current traditional 6-month neutering age of cats was based on the (erroneous) belief that bitches should have one heat prior to spaying - at the time cats were considered to be small dogs in veterinary terms! Years ago, when safe paediatric anaesthetic techniques were not available, waiting until a patient was older increased the safety of surgery. This is no longer the case. There is little scientific basis for selecting 6 months as the most appropriate time for neutering since many animals are not sexually mature at 6 months and hence vets are already practising early (pre-pubertal) neutering!

M.A. Herron of Texas A&M reported in 1972 that neutering before sexual maturity had little effect on the diameter of the urethra in male cats (an oft-used argument against early neutering). More recent studies at Angell Memorial Hospital in Boston, the College of Veterinary Medicine at the University of Minnesota, and the Department of Small Animal Clinical Sciences at the University of Florida (Winn Feline Foundation study) uphold this. Animals involved in the Winn study have now been followed for over five years, with no negative side effects reported.

The Winn Feline Foundation’s ongoing project on "Early Spay/Neuter In The Cat" (1) highlights developmental factors of early neutering allaying the most commonly voiced objections. The study bred kittens especially for the project, to limit background influences and genetic variation. The kittens were divided into three groups:

Group 1 (11 kittens) were neutered or spayed at 7 weeks. Surgery was straightforward and uncomplicated, and the kittens recovered more rapidly than Group 2 and Group 3 individuals.

Group 2 (11 kittens) were neutered or spayed at 7 months; the ‘traditional’ age.

Group 3 (the control group of 9 kittens) were not neutered until maturity and after the completion of the first phase of the study at 12 months.

Opponents of early neutering cite possible detrimental side effects of early neutering: lethargy, obesity, stunted growth, cystitis/urinary blockages in males, behavioural effects, food consumption and dietary requirements. Investigators studied weight and body composition (% of body fat); bone length and the age of physeal closure (cessation of long bone growth); behaviour; food consumption; development of the urinary tract, development of secondary sexual characteristics and degree of sexual maturity.

Weight comparisons showed some differences between the three groups. Males consistently weighed more than females. Group 1 and 2 cats had identical % body fat and were generally fatter than Group 3 cats (neutered after sexual maturity). By 12 months, Group 3 males exhibited the normal adult male characteristics of decreased weight and the development of jowls, accounting for some of the differences. In the course of follow-up, the weight differences between cats from Groups 1 and 2 and Group 3 became less apparent. After 7 months, the unneutered cats in Group 3 were less affectionate and more aggressive. Contrary to popular opinion, neutered animals were as active as their unneutered age mates. All cats were placed in supervised homes where they are more active than they were in the University facilities.

There was generally no difference in food consumption between the three groups nor any difference in growth rates, although the males in all groups grew faster than females. Increased long bone length occurred in both males and females in Groups 1 and 2 due to delayed closure of the bone growth plate. Early neutered cats, especially males, are frequently longer and taller than unneutered/late-neutered cats rather than stunted.

There was no difference in urinary tract development between the three groups other than normal gender-related differences. The diameter of the urethra in the male kittens was not different. i.e. early neutering did not result in smaller diameters in the urinary tract, nor an increased incidence of cystitis and related problems. Concerns that development of the female urinary tract might be arrested or impaired by early spaying and neutering also proved unsupported.

The results indicate that differences between cats neutered at 7 weeks and 7 months are insignificant. The differences observed do not affect the health of the animal in a negative way and the indications are that early neutering is not detrimental to the overall health of the animal.

Early neutering as a form of population control

From the perspective of shelters the results of early neutering studies are encouraging. If all kittens adopted from shelters, are neutered prior to adoption, there should be a corresponding decrease in the numbers of ‘surplus’ animals euthanased. Preliminary results from Alachua County, near the University of Florida at Gainesville, support this. The American Humane Association has endorsed early neutering as a "feasible solution to decreasing pet overpopulation and the tragedy of resulting deaths" and the Cat Fanciers' Association (CFA) has changed its show rules to permit neutered kittens to compete.

In a report (2) delivered to the 18th Annual Feline Symposium (1996) Dr. Thomas Lane, presented further data which supported the initial findings that there were no differences between Groups 1 and 2 and that the slight differences between Groups 1 & 2 and Group 3 equalised over time.

Dr. Lane promotes neutering as early as six-seven weeks of age, with no evidence of any increased incidence of disease or interference with the immune system. Neutering at about six months of age, as is currently practised, is already pre-pubertal in many cases. He addressed the concern of stunted growth. Since the absence of oestrogen and testosterone delays closure of the growth plates, early neutering actually results in larger cats, not stunted growth. To date he has found no increased risk of urinary incontinence, nor anaesthesia problems, nor decreased bone strength, nor decreased immune response.

Very important work has been done by Drs. Michael Aronsohn and Alicia Faggella at the Massachusetts SPCA on anaesthetic and surgical techniques for early neutering of dogs and cats (4, 5). In 1993, two papers were published outlining their work on the early neutering of hundreds of kittens between the age of 6 and 14 weeks. They evaluated several anaesthetic protocols and made recommendations for safe handling and anaesthesia in patients of this age. Some small changes to surgical technique are necessary and young patients must be handled a bit differently both before, during, and after surgery, however, the experience of these veterinarians is overwhelmingly positive.

Contraception vs neutering

Contraception addresses the reproduction issue, but does not address other issues. Oral contraception must be administered regularly in food. The dosage is difficult to work out if the cats scavenge food elsewhere. Where there are several cats, those feeding first get high doses of the contraceptive while those feeding later may get an insufficient amount. Studies showed that female cats may suffer from endometritis or pyometra, conditions which may actually be caused by hormonal contraception (3). Contraceptive implants are used in lionesses and may be feasible in cats, however, but humans females have recently been reporting problem side-effects with implants. Another drawback with contraceptives, either using hormones or antibodies, is that they may not remove the mating urge and therefore may not reduce the risks of diseases and injuries to which entire cats are more prone than neutered cats are exposed.

For tomcats, vasectomy leaves them reproductively sterile but behaviourally intact - they continue to spray and roam. Animal charities are not attempting to encourage intolerance of the sounds and smells of intact male cats - they are trying to cope with the number of intact males whose owners have already demonstrated intolerance of tomcat habits; and with intact toms which have strayed so far from home in search of a mate that they have become lost (most are never claimed). It is incorrect to suggest that alternatives have not been investigated. None of the current alternatives are as reliable or well understood as neutering. The one-shot, lifetime-long contraceptive vaccination is still some way off although initial studies have commenced. In the meantime neutering is required to prevent excessive population growth.

Hazards associated with not neutering

Intact toms are at greater risk of testicular cancer and to prostate problems which can be severe enough to prevent passage of urine, leading to a ruptured bladder and death.

Intact (or vasectomised) toms fight over territory and over the right to mate a female. It is a part of being a testosterone-fuelled cat. In fighting, they spread and contract incurable FeLV and FIV. There is no vaccine for FIV. Neutered toms are far less likely to fight and these risks are much reduced. Fight wounds can lead to blood poisoning, abscesses, the loss of eyes or ears and wounds can be life-threatening. What responsible owner wishes to expose their cat(s) unnecessarily to life-threatening wounds and fatal diseases in the erroneous belief that they are being humane by not neutering the cat?

Intact (or vasectomised) toms roam widely in search of mates. Many of the cats killed on roads are unneutered toms. Others are maimed and die slow deaths, too far from home to be found by their owners. Injured cats often seek secluded places (their instinct to avoid being found by predators) and if found, are often beyond help. Those that are found may require amputation of a limb, removal of an eye or be brain-damaged due to head injuries. Neutered males are far less likely to roam and consequently at less risk of a premature death on our roads or being permanently crippled by injuries sustained while seeking a mate. Those owners who do not believe in neutering often don’t bother about vet treatment for injuries or fight wounds and almost all cat shelters have encountered toms with truly horrific fight wounds, often necessitating euthanasia.

The alternative is confinement indoors which X considers unnatural. Frustration of the mating instinct is stressful for the cat. Few owners are tolerant enough of tomcat odour to do this. Those that keep entire toms as indoor-only pets do not usually have many visitors and, though I hate to say it, you can usually smell the owner of an entire tomcat from a good way off. Even if the cat’s owner is prepared to tolerate the natural sound and smell of her tomcat, neighbours are usually less understanding and may even cause injury to the cat should it enter their property.

The population density of domestic cats is unnaturally high compared to wild animals (e.g. several cats in one street) and if tomcats are not neutered and kept in close proximity, the effect is little different to pitting fighting cocks together - they fight. Keeping multiple intact males together in a multi-cat household and allowing them to fight it out on a regular basis is obviously stressful and, should they continually fight, cruel. Even keeping them separated in a multi-cat household is stressful because their instincts are frustrated. The only humane solution is to remove the urge to fight each other.

Unspayed females may indeed have their reproductive capacity controlled by non-surgical means, however, they an unspayed female is still at increased risk of womb infections which will require emergency hysterectomy in order to save the her life. They are at greater risk of mammary cancer. Failure to treat these conditions in a pet cat constitutes cruelty. Pregnancy in older females is additionally dangerous - in the natural state a cat does not survive long enough for a late pregnancy; however domestic cats live longer than feral or stray cats which is another factor in population increase (as it is in the human population).

Even if unable to reproduce, females may continue to mate. Part of mating involves the tomcat using the ‘neck-bite’ which can, and often does, break the skin. I have seen extensive scabbing on the neck in one female cat who was frequently mated (to the point of exhaustion) by several toms. FeLV and FIV can be spread from male to female by this neck-bite.

Anti-neutering - implications for feline welfare

Do those who oppose neutering care so little about their cats’ health and welfare that they do not wish to reduce the hazards listed above? Do they care so little about cats in general that they want to make the tabloid prophecies of a ‘cat plague’ (and of anti-cat sentiments such as are found in parts of Australia) come true so that no-one is allowed to enjoy the companionship of creatures which choose to live in our homes or so that all cats must be confined indoors for their entire lives so as not to cause a nuisance to others or to the environment? Those who promote a ‘natural’ and unneutered lifestyle will move us inexorably closer to a scenario where no cat may enjoy the outdoors. There are already those who voice strong anti-cat sentiments in Britain and who view the proposals of the anti-cat lobbyists in Australia as desirable in Britain.

One misguided exponent of 'natural methods' and non-neutering pleaded with owners to leave their cats' reproductive capacities intact so that they could pass on their valuable genes. The writer did not, however, discuss the matter of over-population and gave information on destruction of unwanted kittens. It is more humane to prevent the birth of unwanted kittens than to allow cats to produce litter after litter and then to destroy kittens. The reproduction-destruction philosophy is a return to the unenlightened days of drowning kittens and a drain on the female cats' strength (continued reproduction is associated with decreased life expectancy - it's wear and tear on a cat's body).

No-one has written in this publication (the feline-oriented journal in which the original letter and this response appeared) that cats are here to be of service to humans. However, humans have removed the cat from its natural state. Our domestic cat is of African descent, it is not (as X implies) a tame version of the intractable, indigenous Scottish Wildcat. We can either let cats reach such numbers that more people become so intolerant of them that they call for eradication, as is happening elsewhere, or we can accept responsibility for keeping their numbers under control in order to avoid the use of traps, poisons and mass-extermination. Consider those Mediterranean countries where neutering is not performed. Every so often someone will collect up however many kittens they can catch (which can include pet kittens which have ventured outdoors) and dispose of them by drowning or simply dumping them in a plastic bag in an industrial-size waste bin. Adults are routinely poisoned with strychnine; it can take them several days to die and it has caused the death of dogs and birds of prey. I spent some time in part of Brittany, France where it was common practice and quite acceptable to poison cats. Without neutering, the British feline population would increase to such a point where similar methods of population reduction might be considered necessary or would be used regardless of the legality of the method.

A person who holds their cat in high regard as a companion which chooses to live in their home will also want to reduce the risk of premature death from traffic, FIV, FeLV, maiming, septicaemia, pyometra etc as well as accepting the need to prevent feline over-population. Overpopulation devalues the quality of life for all pets. A neutered cat is not only likely to be a calmer, healthier, more content pet; its life expectancies is about twice that of unspayed/unneutered cats; with greater quality of life due to reduced risk of injury or illness.

Unowned cats and natural lifestyles

In not accepting that an unowned cat is an unwanted cat, X makes no distinction between unowned as in ‘stray’ or ‘abandoned’ and unowned in the sense of ‘feral’. What does ‘abandoned’ mean if not ‘unwanted’ and ‘unowned’? It would be facetious to suggest that the cats which are left on rescue shelter doorsteps in boxes are gifts from well-wishers. It is pointless to argue that unowned cats are wanted cats if no homes can be found for them.

While some pet owners claim that they have no trouble giving away their kittens, they should realise that their ‘babies’ take homes away from other unwanted kittens. Kittens deliberately bred by opponents of neutering occupy homes that could have taken in homeless animals already born. Also, if they were to call the adoptive homes one year after the adoption, they might be surprised to find that very few kittens still live with the families that adopted them. Pedigree cats do not compete with moggy cats for homes. Many people own purebreds and moggies. Those who buy purebreds and who do not want moggies would, in all probability, have gone without cats completely if the purebreds did not exist hence the pedigree cat has not denied a mixed breed cat a home

It is not true that rescue centres refuse to accept kittens because they don't care about kittens. X suggests that the main reasons people with kittens are asked to hold onto the kittens until they can be homed is so that rescue centres don’t have to care for the kittens. Kittens should not be homed before the age of 8 weeks (12 weeks is preferable, but this is not an ideal world). Attempting to place kittens at shelters at the age of 6 weeks, or even 4 weeks (as some cat owners do) is stressful to kittens. Stress can adversely affect their immune systems and their overall development. It is, of course, convenient for moggy breeders that early separation may cause the female to come into oestrus ('on heat'), allowing her to be bred sooner and increasing the number of kittens she produces in a single year. I have seen female cats who have lost the use of their hind legs (atrophied muscles) due to repeated breeding this way.

Space at shelters is genuinely limited and unless people do accept the need to have cats neutered space will become more and more limited. Homing a kitten from its own home is less traumatic than bringing it into a shelter and then rehoming it, thus exposing it to the stress of two ‘rehomings’ in a short period of time.

X implied that shelters won't rehome cats to indoor only situations so that moggy-breeders must compensate for this perceived fault. Contrary to X’s beliefs, many rescue shelters do home cats to people living in flats and I am aware of plenty of contented indoor only cats, but once again, how many people living in flats wish to share their home with an unneutered tomcat? Shelters also ask that those in flats or other rented accommodation check that their leases permit the keeping of cats, something that few moggy-breeders do (for them it is more important to offload the kittens).

Devaluing the natural cat?

The writer asks us to appreciate the value of the ‘natural cat’. Except for ferals, cats are domestic animals choosing to live in our homes. Domestication took these animals out of their own natural ecosystem and environment thousands of years ago (2000 BC approx in Ancient Egypt, probably earlier in the Indus valley [now Pakistan]). Their reproduction is no longer regulated naturally by predators or habitat. Their numbers are no longer controlled by predation upon kittens or upon weaker adults. They ceased to be truly wild many generations ago; indeed many no longer hunt because this instinct is reduced (I write from experience).

In return for accepting cats' companionship we must accept the responsibility for caring for them, not only by feeding them but also by not allowing their population to exceed our capacity to care for them. Allowing them to fall victim to traffic or disease is not a humane or reliable means of population control; many of the cats which die this way may be loved pets whose owners may have been ignorant of the benefits of neutering or who have been persuaded against neutering by less-than-rational arguments. Neutering controls the population and reduces health risks and hazards to which intact cats are exposed, not because they make a considered choice, but because of hormonally driven urges.

I would also like to point out that early neutering of feral cats actively allows them to return to their natural state i.e. the state into which they have been born. However, it is not a matter of choice for a kitten to be born feral or tame.

If humans are well-meaning enough, as many are, to feed a feral colony (permitting it to reproduce beyond the available natural resources) then humans must also accept responsibility for ensuring the cats’ health in other respects, including neutering. Where feral cat numbers are not stabilised by neutering, the population reaches problem levels with spraying and cat faeces posing not only a nuisance, but also hygiene and health risks to humans. Calls for population reduction or wholesale extermination invariably result. In many cases, people are willing to accept a smaller colony of healthy, neutered cats where they would not accept a large colony of starving, diseased or injured ferals and dying kittens. Neutering allows these cats a reasonable quality of life and permits them to coexist with humans without posing health risks. Not neutering all-too-often condemns the entire colony - healthy individuals as well as injured, malnourished and diseased cats.

Unfortunately there are too many owners who care too little about their cats’ health and physical and psychological welfare to have them neutered. Or perhaps they misguidedly believe themselves to be well-intentioned; governed by emotional rather than rational arguments and anthropomorphising their cats. Cats do not have recreational sex as do humans. Such owners expose their own cats to unnecessary hazards and apparently prefer stray and feral cats to die unpleasant deaths rather than have their population limited to so that the cats can enjoy a better quality of life. It is because of refuse-to-neuter owners that early neutering must be considered by those who put feline welfare foremost.

Neutering remains the most effective means of population control, but delaying the surgery long enough for sexual maturity to occur defeats the purpose. Early neutering is a safe and effective means of ensuring we do not unwittingly add to the burden of unwanted pets.

Cats are not Dogs!

On balance, the benefits of neutering outweigh the risks. Neutered cats live longer and are more likely to find, and remain in, homes. The "homeability" resulting from neutering should not be under-estimated. Neutering, like any other surgical procedure, carries a risk of complications due to use of general anaesthetic and possible surgical complications, such as bleeding and infection. These risks are relatively low, but may be increased if the animal has other health issues. In one study the risk of anaesthetic-related death (not limited to neutering procedures) was 0.11% (about 1 in 1000) for healthy cats and 1.40% in cats with existing health issues.

There has been a recent tendency to argue against feline neutering based on problems encountered in neutered dogs. In general, dogs appear to risk greater side-effects than cats and some cat owners misguidedly use dog-related arguments to support their anti-neuter stance. There are important difference between the species: female dogs come on heat periodically while female cats cycle continuously and only ovulate after mating (almost guaranteeing pregnancy). Unlike spayed bitches, spayed cats don't appear to develop oestrogen-responsive conditions such as incontinence or vaginitis. Many of the reported neutering-related problems in dogs relate to underlying breed predispositions exacerbated by neutering and have no equivalent bree predispositions in cats.

Spaying eliminates oestrous behavior in females and means roaming males will not be attracted to her home. A female on oestrus may call loudly for a mate, may spray (to advertise her availability) and may solicit other pets to mount her. This behaviour can become frantic and an unmated female will go back on oestrus within just a few days. As well as preventing unwanted pregnancies and pregnancy/birth related risks, spaying eliminates ovarian/uterine diseases and greatly reduces the incidence of mammary cancer. Pyometria (infection of the womb) is not uncommon in unspayed, unmated cats and can be fatal. Because the tomcat can break skin when he grips his mate by her scruff during mating, unspayed females are at greater risk of FIV and FeLV. Hysterectomy, without removing the ovaries, prevents conception but doesn't protect against mammary cancer, womb infection or prevent calling for a mate.

Uncastrated males do not generally make good housepets, but castration usually eliminates their antisocial behaviours. It eliminates or dramatically reduces urine spraying and reduces the pungency of the urine (tomcat pee is incredibly pungent compared to neuter-cat pee). It dramatically reduces roaming and inter-male aggression which means far fewer (or no) fight injuries. This prevents the spread of infections and viral diseases transmitted through bite wounds. Vasectomy, while possible, will not prevent antisocial behaviours or prevent testicular tumours. However, compared to intact males, male neuters have an increased risk of feline lower urinary tract problems, including urethral blockages due to stones forming in the urine. Blockages are more common in cats fed a dry food diet, but modern formulations better control the pH of the urine (canned food has a higher moisture content, resulting in more dilute urine and less risk). Some cats, regardless of neuter status, have a genetic predisposition to develop urinary blockages and surgery is an option.

Sex hormones produced by the ovaries and testes also have other effects on a cat's body. They affect on energy metabolism, but play only a minor role in appetite and body weight. Unneutered cats, both male and female, have higher metabolic rates than neutered cats, but boredom, overeating and lack of exercise are the main culprits in feline weight gain. Unneutered cats are geared to burning off calories roaming, fighting and breeding; neutered cats need alternative forms of exercise. The steroid hormones produced by the gonads also contribute to maintaining bone density, fat/muscle ratio, cognition, behaviour and the immune system. There is much data about possible adverse effects of spay and neuter in dogs, but no comparative detailed studies for cats. There are few veterinary reports of increased risk of osteoporosis in neutered cats and although elderly neutered cats may develop senility (cognitive deterioration), unneutered cats rarely live long enough to become senile - the senility in neutered cats is due to their longer lifespan.

Rather than basing an anti-neutering argument on data from dogs (and often breed-specific data at that), any studies/arguments comparing disease risks for neutered and unneutered cats must take into account the following:



(1) Developmental and Behavioral Effects of Prepubertal Gonadectomy. Mark S. Bloomberg, DVM, MS; W.P. Stubbs, DVM; D.F. Senior, BVSc; Thomas J. Lane, BS, DVM; University of Florida at Gainesville. Funded by the Winn Feline Foundation, February 1991. Continuation funded February 1992. A progress report on a study funded by The Winn Feline Foundation (Summary prepared by Diana Cruden, Ph.D. 1995/1996)

(2) Report from The 18th Annual Feline Symposium, June 13, 1996 Chicago, Illinois on Prepubertal Gonadectomy (Early Spay & Neuter). Thomas J. Lane, DVM Summary by Brian Holub, DVM

(3) The Wildlife of the Domestic Cat 185-186, Roger Tabor; Arrow Books 1993.

(4) Aronsohn MG, Faggella AM. Surgical techniques for neutering 6- to-14-week-old kittens. Journal of the American Veterinary Medical Assoc Vol 202(1);53-55, 1993.

(5) Faggella AM, Aronsohn MG. Anesthetic techniques for neutering 6-to-14-week-old kittens. Journal of the American Veterinary Medical Assoc Vol 202(1);56-62, 1993.

Further Information on Early Spay/Neuter:

Chalifoux A, Niemi G, Fanjoy P, Pukay B. Early spay-neutering of dogs and cats (letter). Canadian Veterinary Journal Vol 22; 381, 1981.

Hosgood G. Anesthesia and surgical considerations in Hoskins JD (ed) Veterinary Pediatrics - dogs and cats from birth to six months, Philadelphia, WB Saunders Co., p. 561, 1995.

Lieberman LL. Advantages of early spaying and neutering (letter). Journal of the American Veterinary Medical Assoc Vol 181(5);420, 1982.

Lieberman LL. A case for neutering pups and kittens at two months of age. Journal of the American Veterinary Medical Assoc Vol 191(5);518-521, 1987.

Root MV, Johnston SD, Johnston GR, Olson PN. The effect of prepuberal and postpuberal gonadectomy on penile extrusion and urethral diameter in the domestic cat. Veterinary Radiology & Ultrasound Vol 37(5);363-366, 1996.

Stubbs WP, Bloomberg MS. Implications of early neutering in the dog and cat. Seminars in Veterinary Medicine and Surgery (Small Animal) Vol 10(1);8-12, 1995.

Stubbs WP, Salmeri KR, Bloomberg MS. Early neutering of the dog and cat in Bonagura JD, Kirk RW (eds) Kirk's Current Veterinary Therapy XII Small Animal Practice, Philadelphia, WB Saunders Co., p. 1037, 1995.

Theran P. Early-age neutering of dogs and cats. Journal of the American Veterinary Medical Assoc Vol 202(6);914-917, 1993.

Additional References and Further Reading