Neutering Your Pet

Neutering your Pet

There are many reasons why you may be thinking about neutering (spaying or castrating) your pet/s. This page considers these reasons and looks at surgical and medical options.

​What is neutering?

Neutering means surgically removing the reproductive organs in your pet, to prevent them for reproducing. In male animals this is termed "castration" and in females we call it "spaying". Medical castration of male dogs using an implant is also possible and becoming increasingly popular.


​What is involved?

Surgical neutering, regardless of what companion animal you have, is carried out under a general anaesthetic. Every surgical procedure carries some risk, but modern techniques are very safe. In males for a castration, both of the testicles are removed, for ferret vasectomy a section of the spermatic cord is removed but the testicles are left in place. In females, both ovaries are removed with or without the uterus, at Holmer we routinely perform ovariohysterectomies removing both the ovaries and the uterus. All surgical procedures will carry some level of discomfort, but your pets will have pain relief given and usually they are up and about within a few hours of their procedure.

Chemical castration can usually be performed without the need of an anaesthetic in male dogs during a routine consultation. An implant, much like a microchip, is placed under the dogs skin, similar to surgical castration this should be done at the time of sexual maturity (6m+ in small breeds 12m+ in large breeds). There are two sizes of implant available one with a duration of effect for 6-12months the other 12-24months. As the therapy takes effect, within 4-6 weeks, the dogs testicles shrink down and the dog becomes infertile, for an individual evidence that the implant effects are wearing off can be determined by detecting that the testicles are getting bigger again. Side effects of the implant are considered very rare with potential transient increase in sexual behaviour, testicle size with or without some discomfort, or transient behaviour changes. The implant may be used in prepubertal bitches at 12-16 weeks to postpone the first season but cannot be used to control seasons in a sexually mature female due to a high risk of significant adverse effect. In ferrets the implant is usually administered under sedation or anaesthesia with effects lasting up to 18months.

What are the potential benefits and risks of getting your dog neutered?

For male dogs:

  • lower testosterone levels mean neutered dogs are less likely to show aggressive behaviours towards other dogs, less likely to provoke aggression from other dogs and are less likely to show sexual behaviours such as "humping"
  • they are also less likely to roam - which is often when they go missing/get involved with accidents
  • unneutered male dogs can get frustrated when they smell a female in season, and can try to escape or act in strange ways
  • castration significantly reduces the chance of getting prostate disease.
  • eliminates risk of testicular cancer

When should I neuter my dog?

  • For males we advise waiting until they are at least 6 months old, however this does depend on their breed.
  • For larger breed dogs we prefer to wait until their bones have stopped developing, at around a year old.
  • Your vet can advise you what is best for your dog.

For Female dogs:

  • removal of the ovaries takes away the hormones that cause female dogs to come into season, so they will no longer come in heat
  • spaying prevents unwanted pregnancy
  • spaying early in life dramatically reduces the chance of developing breast cancer
  • spaying eliminates the chance of developing a pyometra - a potentially life threatening infection of the womb.
  • Spaying eliminates the risk of ovarian cancer and reduces the risk of uterine cancer.

When should I neuter my female dog?

  • At Holmer, we generally advise spaying 12 weeks after your dog has had her first season - which can happen, on average, between 6-12months of age. If an owner feels they need to spey a bitch before their first season they should discuss this with a vet.
  • For larger breed dogs ideally we would wait until after they are 12 months of age, as larger breeds tend to have their first season later this is still usually after their first season.

Potential negative effects of neutering

  • New evidence suggests that neutering nervous aggressive dogs can make their symptoms worse especially human focused aggression so it is advised these are addressed before proceeding with neutering. This is less likely with chemical castration.
  • There are now questions over whether there is an increased risk for certain cancers in surgically neutered pets which does not appear to be an issue when medically/chemically castrating.
  • Surgically neutered pets are more prone to weight gain as their metabolic rate can be reduced by up to 30%. It is important to manage/potentially reduce their food intake as appropriate. Your vet or veterinary nurse will happy to discuss diet and weight management with you if you have any concerns.
  • Spayed females may develop urinary incontinence (leakage of urine), if this occurs it can usually be managed with medication.
  • Some pets may develop a change in coat texture.

Why should I get my cat neutered?

Reasons for neutering female cats:

  • Population control: cats can have their first season at around 6 months of age, possibly earlier, and can have 3 litters every year. There is absolutely no benefit to your cat allowing them to have "just one litter" and pregnancy does carry a degree of risk to your cat. On top of this it wouldn't be good to contribute to the thousands of unwanted cats already needing homes.
  • Control of seasons: when female cats come into season they will "call" for mates - which can often be a bit distressing and also will attract entire males to your house - causing issues such as spraying and fighting. Spayed females do not come into season
  • Health: other than the potential health risks related to pregnancy and having kittens itself, spaying also eliminates the chance of pyometra and when performed before 6months of age drastically reduces the chance of mammary cancers.
  • Welfare issues: unwanted kittens are more likely to be at risk of infections such as cat flu, and there are unlikely to be enough homes for them.

When should I neuter my female cat?

  • We advise neutering female cats at 5-6months old, when they have reached a minimum weight of 2kg, before they start coming into season.

Reasons for neutering male cats:

  • Population control: one male cat can mate with multiple female cats and result in huge numbers of unwanted kittens.
  • Health issues: entire males are much more likely to fight, resulting in infections and abscess, and fighting males are more likely to spread incurable diseases such as FIV and FeLV
  • Nuisance control: entire males stray over large areas and spray urine to mark their territory - which is very smelly. they are also more likely to fight which can be very noisy.
  • Pet issues: entire males are more likely to stray from home and not return. They are more likely to spray urine in the home which is very unpleasant. They are more likely to be aggressive to owners.

When should I neuter my male cat?

  • It is preferable to neuter male cats at 5-6months old, before sexual maturity, to prevent these issues.
2 rabbits


For the best health and welfare rabbits should be kept in bonded pairs ( When a female + male bonded pair (often most suitable pairing) neutering prevents unwanted pregnancy. When same sex pairings are made (2 males or 2 females) neutering both rabbits reduces the risk of inter rabbit aggression. Neutering of female rabbits also reduces the risk of mammary and uterine cancers, and eliminate the risk ovarian cancer.


It is not recommend to surgically neuter ferrets as this can result in them developing a potentially life-threatening hormonal condition known as Cushings.

However, hormonal management in ferrets is important.

Male ferrets can be medically castrated using a hormonal implant that can last up to 4 years this can help reduce aggression and may enable such make ferrets to be housed together. Alternatively male ferrets can be vasectomised, where part of the tube that carries the sperm is removed to prevent fertilisation occurring. Vasectomised ferrets still have all their hormones so still act as an uncastrated male. Vasectomised ferrets are often used in the management of female ferret hormone cycles.

Female ferrets (jills) are induced ovulators, they need a male ferret to stimulate them to ovulate/release eggs from their ovaries. If they do not receive this stimulation the hormone oestrogen remains high and can cause potentially life threatening bone marrow suppression. Female ferrets can be put with vasectomised males to stimulate them to ovulate and keep them healthy. Alternatively, hormonal implants can be used (off license) to prevent cycling for up to 18months. Hormone injections, given to a jill as soon as she was seen to come into season used to be popular but are no longer available.

Ferret climbing inside a cage.
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