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Castration is the surgical removal of a male animal’s testicles. It is also known as neutering, sterilisation, “fixing”, desexingsnipping or by its veterinary names – orchiectomy and gonadectomy. During the procedure, each of the animal’s testes and testicular epididymis are removed, along with sections of testicular blood vessels and spermatic ducts (vas deferens or ductus deferens). The parts removed are responsible for sperm production, sperm maturation and the secretion of testosterone (the major male hormone).

Generally, castration has numerous advantages and disadvantages which we shall now discuss.

Behavioral advantages of Castration

To prevent unwanted litter and population control: Irresponsible pet ownership leads to overpopulation of pets, and dumping/abandoning of unwanted litters of puppies and kittens. Every year, thousands of unwanted dogs and cats roam the streets or are abandoned on the street, and they eventually become nuisances and health threats to people in the neighborhoods. This sad waste of healthy life can be reduced by not letting pet dogs and cats breed indiscriminately. Therefore, one way of preventing any accidental, unwanted breeding from occurring is through the routine neutering of all non-stud (non-breeder) male dogs and tomcats.

Decreased testosterone-induced behavior: One of the most important behavioral advantages of castration is that castrated dogs and cats tend to be less aggressive as adults towards their male counterparts and towards people.  Complete dogs and cats are likely to be more aggressive, more dominant and more prone to male-to-male aggression (inter-male aggression) and fighting than neutered animals are. They will also tend to exhibit sexualized behaviors including: aroused interest in females of their own species; mounting of females (particularly in-heat, estrus females) and mating of females. Furthermore, they are more prone to displaying unwanted masculine territorial behaviors such as the guarding of resources (food, territory, companion people and so on) and the marking of territory with urine and feces (e.g. entire tomcats will commonly exhibit urine spraying in the house. The testicles are responsible for producing testosterone – the hormone that makes male animals look and act like male animals. And once neutering is done, production of testosterone is greatly reduced, and subsequently, aggressive behavior is equally eliminated or reduced.

Decreased roaming and stray animals: Male dogs and cats can sense females in heat through pheromones which leads to a behavior called “roaming”. If dogs and cats are castrated at an early age, they will not sense or respond to pheromones, and would certainly be less stressed and tend to stay home during mating seasons. On the other hand, complete male animals are more likely than neutered animals to leave their compounds or yards to roam the streets looking for females and for trouble. Roaming is a troublesome habit because it puts other animals (wildlife and other pets) and humans at risk of harm from your pet and it puts the roaming pet at risk from all manner of dangers including: predation by other animals, cruelty by humans, poisoning, envenomation (e.g. snake bite) and motor vehicle accidents. Castration may reduce some of these problematic testosterone-mediated behaviors.

Increased concentration and obedience: This is another behavioral advantage that is useful for when you are training or working your dog or cat, or using him for field work. If castrated, he will be a much better student with a much longer attention span even when there are females nearby that are in heat. This is because he will not be constantly distracted by pheromonal stimuli.

Medical advantages of castration

No testicular tumors: There are several different tumor types, both benign and malignant, that arise within the testicles. As with most cancers, these usually are not noted until the animal reaches 5 or more years of age. Therefore, these would not be a problem in those dogs and cats that have been castrated at the recommended earlier age.

Improved genetics: We can all agree that a male carrying a harmful genetic trait like hip dysplasia or epilepsy should be castrated. We must do all that is possible to prevent the spread or continuation of these conditions and others like them. Dog or Cat breeding is not merely the production of offspring, it is the transferral of genes and genetic traits from one generation to the next in a breed population. Pet owners and breeders should castrate male dogs and tom cats that have traits that are unfavourable or faulty to the breed as a whole and to reduce the spread of these defects further down the generations. Also, male dogs and cats with inheritable genetic diseases and congenital defects/deformities should also be neutered to reduce the spread of these genetic diseases to their offspring. Some examples of such inheritable diseases include cryptorchidism, polycystic kidney disease (PKD),lysosomal storage diseases and amyloidosis.

Fewer incidence of hernias: a hernia is a protrusion of an organ or parts of an organ or other structure through the wall of a cavity that normally contains it. Perianal hernias occur when the colon, urinary bladder, prostate, or fat protrude from the abdominal cavity, through the muscular wall by the anus and then lie just under the skin. This type of hernia is far more common in older, unneutered male dogs. The levels of testosterone and other hormones appear to relax or weaken the group of muscles near the anus. When the animal then strains to defecate or urinate, the weakened muscles break down and the abdominal organs and fat bulge out under the skin. Left untreated, these organs may become damaged, unable to function or even die from loss of blood supply. Additionally, because of the displacement of organs into this area, the animal may not be able to defecate or urinate correctly or completely and may become constipated or have urinary incontinence (dribble urine).

Prevention or reduction of testosterone-induced diseases It is well known that complete dogs can suffer from a range of diseases and medical conditions that are directly associated with high blood testosterone levels. These disease conditions include benign prostate hyperplasia (BPH), prostatitis, prostatic abscesses, perianal or perineal adenomas (small cancers that occur around the anuses of entire male dogs), perineal hernias and certain castration-responsive skin disorders (dermatoses). Castrating these dogs removes the main source of testosterone from the animal’s body (the testes), which not only prevents the onset of these diseases but can even help to control or cure these diseases if they are already present. In cats however, these diseases are not that common so its not always a reason for castration

The reduction of tom cat urine odors
People with inside cats often have to put up with smelly urine and fecal odors coming from their cats’ litter boxes or even around the house if/when they pee. As owners of complete tomcats can attest to, this urine smell can be very pungent and noxious, heavy with the stench of male cat pheromones. The odor is the result of testosterone and the retrograde ejaculation of sperm into the bladder. However, neutered male cats do not seem to produce this pungent urine smell. Therefore, castration can be considered a means by which owners of house cats can seek to reduce litter box urine odors. As an added bonus, castration will sometimes cure inappropriate spraying and toileting behavior in some tomcats altogether.

Disadvantages of castration

The cat may become overweight or obese:
Studies have shown that castrated animals probably require around 25% fewer calories to maintain a healthy bodyweight than entire male animals do. This is because a castrated animal has a lower metabolic rate than an entire animal does (it therefore needs fewer calories to maintain its bodyweight). Because of this, what tends to happen is that most owners, unaware of this fact, continue to feed their neutered tomcats the same amount of food after the surgery that they did prior to the surgery, resulting to fat, sometimes obese pets.

Castration/Neutering means a loss of breeding potential and valuable genetics:
If a dog or cat is the ‘last of its line’ (i.e. the last puppy or kitten in a long line of pedigree breeding animal), castrating that animal will lead to loss in valuable breed genetics. This will essentially spell the end for that breeding lineage.

Immature development of masculine characteristics and a reduced body musculature
The testicles are responsible for producing testosterone: the hormone that makes male animals look and act like male animals. It is the testicles that make male animals develop the kinds of masculine, testosterone-dependent body characteristics normally attributed to an entire animal. These include: increased muscle size and development; reduced body fat; mature penis development; mature prepuce development (mature penis sheath development); the ability to extrude the penis from the sheath (prepuce) and the suppression of development of feminine characteristics (mammary gland development, milk production etc.). Castration, particularly early age castration, may limit the development of mature masculine features such that they remain immature and juvenile looking and cause the neutered animal to have a reduced muscle mass and strength compared to an complete animal of the same size and breeding.

Castration may result in delayed growth plate closure
Animals that have been castrated early in life (before the age of 12 months) tend to exhibit delayed closure of their growth plates. Growth plates are the cartilage bands located in the ends of the animal’s long bones, which are responsible for making the bones grow and elongate during juvenile bone development and formation. As a result of delayed growth plate closure, castrated animals will often be taller and longer in limb than entire male animals. Whether this increase in growth plate closure time or bone length should be considered a problem or benefit really depends on the individual owner, but some people choose not to neuter animals early because of it (i.e. there is a concern that these animals may be more prone to orthopedic injuries). Any concerns about the effects of delayed growth plate closure, while not normally a problem, can be overcome if the castration is done after the growth plates have closed.

Are you curious about how castration (or neutering) works? Watch this video of a dog being castrated by  a veterinarian



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