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Animal neutering

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In the course of castration, the gonads are removed from the animal. This means that they can no longer produce or give birth to offspring.

Animal neutering: what is that?

In a neutering operation, the vet removes the animal’s gonads. In male animals these are the testicles (testes) and in female animals the ovaries. The result of neutering an animal is that it can no longer produce progeny or give birth, that is, it makes them infertile. The same effect can be achieved without surgery by using hormone preparations (known as “chemical neutering”). After the effect has worn off, the animals are fertile again.

Neutering removes hormonal glands at the same time as it removes the gonads: the testicles and ovaries produce sex hormones. Processes in the body controlled by these sex hormones naturally diminish then.

Animal neutering: why is it done?

There are different reasons for neutering animals:

Examples of direct medical reasons include recurrent inflammation in the sex organs (prostate inflammation, pyometra, etc.) or tumours. Male animals with cryptorchidism on one or both sides should also be neutered. In this condition, one or both testicles are located in the inguinal canal or in the abdomen and have not descended correctly into the scrotum. The undescended testicles have a very greatly increased risk of developing tumours, which is why the vet will advise their removal. Since cryptorchidism is usually hereditary, reproduction of these animals should be prevented. You can find out more here: Cryptorchidism in dogs.

Extreme sex-specific behaviour also lessens when animals are neutered. Urine marking and wandering in male cats or severe aggression in male dogs can be curbed. Constant heat or false pregnancy is also halted by neutering.

Neutering is also reasonable for animals if they are kept in mixed groups and should not reproduce. It is often recommended to owners of free-roaming cats so that they don’t suddenly become pregnant when they have been outside.

Since body parts are removed when animals are neutered, it is regarded as an amputation. This is permissible only when there is a reasonable justification.

Animal neutering: what happens

How neutering is performed depends on the animal species and sex. All operations have in common that they are performed under general anaesthetic. Dogs and cats should fast for 12 hours but small mammals can eat until shortly before the operation. Your vet will give you further information if your pet is to be neutered.

Surgical neutering of male animals

It is less complex surgery for male animals as the testicles are readily accessible outside the abdomen. The operation area around the testicles is shaved, cleaned and disinfected. The scrotum is opened with a scalpel and the testicles are exposed. Depending on the technique, the connective tissue sac in which they are located is also opened. (The difference between covered and uncovered castration is that in the covered form the connective tissue sac and therefore the inguinal canal remain closed.) The testicles are tied off with sterile thread and divided. The remaining stump is sutured, and the scrotal sac is sutured shut at the conclusion.

In male cats, the hairs on the scrotum are only plucked. Uncovered castration is usually done in male cats and instead of ligation the spermatic cord and vessels are tied. The scrotum is not sutured either but closes spontaneously immediately after the operation.

Neutering is somewhat more complex when cryptorchidism is present as the testicles have to be removed either from the inguinal canal or abdominal cavity.

Surgical neutering (spaying) of female animals

The ovaries of female animals are in the abdomen, close to the uterus. For spaying, the belly is shaved, cleaned and disinfected. The surgeon accesses the ovaries through a small incision, and these are ligated and removed. After this, the abdominal incision is sutured closed.

For female dogs it is now possible to carry out minimally invasive, endoscopic spaying. In this, the instruments are inserted into the abdomen through very small openings and the neutering is carried out. The advantage is the smaller wound area, which promotes faster healing and causes less pain.

By the way: in female animals, either the ovaries only or the uterus as well can be removed. The latter is necessary if the organ is diseased. Your veterinary surgeon will discuss with you when it makes sense to remove a healthy uterus in an individual case.

Chemical neutering

As mentioned above, chemical neutering involves hormone products. Either as an implant or given regularly in tablet form, they suppress the function of the ovaries or testes, thus making the animal infertile. This effect is reversible as a rule; this means that after the medications are stopped or the implant’s effect has worn off the animal will again bring egg cells to maturity or produce sperm. You will find further information about the individual animal species here:

  • Chemical neutering of male cats
  • Chemical neutering of male dogs

Small animal neutering (rabbits & rodents)

Naturally, dwarf rabbits, guinea pigs and hares can also be neutered. Neutering of small animals is essentially the same technically as in dogs and cats, but adjusted to the size and special features.

Uncastrated male rabbits cannot be kept together. They can become so aggressive together that severe bite injuries occur. Bucks that are to live in a group are therefore neutered. Female rabbits are neutered mainly for preventive medical reasons. When they have been neutered, this prevents false pregnancies or some diseases of the ovaries, uterus and teats. Very aggressive dwarf rabbits are also neutered. (A castrated rabbit does not entirely stop its territorial behaviour but it becomes noticeably calmer.)

Apart from preventive reasons, male guinea pigs would be neutered because of scrotal tumours or abscesses (collections of pus). Female guinea pigs are neutered mainly for medical reasons (ovarian cysts, inflammation and tumours in the uterus).

By the way: small animals can be brought to the practice or clinic the day before the operation. This reduces stress for the animal.

Neutering of animals: what happens afterwards?

After the neutering, the animal will first recover from the surgery. When it has woken up fully from the anaesthetic, you may bring your pet home. The wound will be painful in the next few days and the vet will provide your pet with pain-killers for this. Depending on the operation, it will be necessary to remove sutures after about 10 days. This is not required if dissolving sutures were used. If the wound becomes inflamed, the animal gets a fever or shows similar symptoms of disease, you should always contact the vet again. To avoid inflammation it is also important that neutered animals do not lick and bite at the wound. There are plastic funnels for this that are placed around the animal’s neck (this is not usually necessary for male cats). Female dogs are often given a body stocking that covers the incision.

Neutering of animals: what must I be aware of?

Once your pet has recovered from the stress, you may well notice changes in its behaviour. Neutered male cats usually no longer mark, roam less or reduce their roaming radius outside. Neutered male dogs show hardly any sex-specific behaviour. Bitches are no longer interesting for male dogs and no longer develop false pregnancies, which are very stressful for the affected animals.

Warning: behavioural problems that have nothing to do with hormones but have other causes are not alleviated by neutering.

Because of the lack of hormones, female dogs no longer have a cycle after they have been spayed, and this means that bleeding ceases. Many animals also suffer from overweight more often after the operation as their metabolism changes due to the lacking hormones. Prevent this by adjusting your pet’s diet. Female dogs‘ coats can also change. In addition, they are a little more inclined to urinary incontinence, but this can usually be treated well.

Neutering of animals: when is the best time?

There is no general answer regarding the best time for neutering, so please discuss with your vet what is best for your pet. We have summarised some basic information below:

Guinea pigs: early neutering:

Early neutering of guinea pigs is possible above a weight of 200 g, when the males are about 2-3 weeks old. (As they become sexually mature at about 3 weeks, there are often many unwanted coverings otherwise.) Bachelors/males brought up together usually get on well even if not neutered. If they are to be socialised with females, neutering is necessary.

For all other rodents (degu, chinchilla, rat, mouse, gerbil) please talk to your vet, as sexual maturity differs from one species to another, including in rodents.

Rabbits: early neutering:

Early neutering of buck rabbits is possible at about 9-12 weeks as they are sexually mature from about 12 weeks. The advantage of early neutering is that it is not necessary to separate them from their female partner. “Late neutering“ at 16 weeks or more is a bit easier technically but otherwise offers no advantages.

Female dogs:
If spaying is to be preventive, e.g., against mammary tumours, it is performed between the 1st and 3rd heats. There is further information here: Dog neutering

Male dogs:
Male dogs can be neutered from puppy age onwards. It is usually recommended however to wait until they are fully grown.

If the cat is neutered to prevent reproduction and if the animal has contact with animals capable of reproduction (free-roaming, kept in a group), it should be neutered at the age of 3-4 months and therefore before sexual maturity. Neutering is otherwise possible throughout life. You will find everything else about neutering cats here: Cat neutering

Neutering of animals: risks

Neutering is essentially a routine operation with relatively low risk. Nevertheless it involves a general anaesthetic and an abdominal operation in female animals. Anaesthetic adverse events with difficulty breathing or bleeding can occur. Older animals or those with overweight or a weak heart have a higher risk of problems during or after the operation. Infection and inflammation of the sutures are possible, though they occur rarely.

Neutering of animals: conclusion

Neutering of animals can be necessary for various reasons. Like every operation, they should be considered carefully and not performed thoughtlessly.

Contact a veterinarian


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