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Sterilization (Desexing)

Sterilization (Desexing)

What is sterilization?
A sterilization operation is one where your pet’s reproductive organs (ovaries and uterus in females and testicles in males) are removed so as to ensure that your pet is incapable of reproduction (becoming pregnant in the case of females or impregnating a female in the case of males).

Why should I sterilize my pet?
There are a large number of advantages to sterilizing your pet, some benefiting your pet’s health directly and some which simply make your pet more pleasant to live with. Apart from ensuring that your pet does not contribute to the ever growing unwanted animal population in Singapore (the Society for Prevention of Cruelty Towards Animals in Singapore takes in about 800 unwanted or abandoned animals a month), these are some of the added bonuses when you sterilize your pet:


1) Preventing breast cancer (mammary tumours)

Dogs and Cats: Breast cancer development in dogs and cats is mediated by the hormone, oestrogen, which is produced by the ovaries.

Sterilizing your female dog before her first heat reduces her change of getting breast cancer to virtually zero (0.5%).
Sterilizing her after her first heat leaves her an 8% chance of developing this disease.
Sterilizing her after her second heat causes the risk of breast cancer to jump to more than 1 in 4 (26%).
Every subsequent heat thereafter increases the risk of breast cancer above 26%. It should be noted, however, that sterilization should still be performed even if breast cancer has already developed due to the large role the oestrogen-producing ovaries play in the development and progression of breast cancer.

Breast cancer is the third most commonly diagnosed tumour in cats and female cats sterilized below one year of age are at significantly decreased risk of developing breast cancer.

Rabbits: Further investigation is required to definitively establish a firm link between oestrogen production and mammary tumour development in rabbits, but it is currently believed that desexing in rabbits helps to prevent mammary tumour development.

2) Preventing pyometra (pus accumulation in uterus) and uterine and ovarian cancer

Dogs and Cats: The more heat cycles a dog or cat undergoes, the more likely for bacteria to colonize the lining of the uterine wall. When this occurs, pus develops within the uterus and causes it to expand. This condition causes rapid deterioration in the animal and shock, hypothermia and ultimately death can result in a short span of time. Surgical removal of the uterus at the time of diagnosis is the only reliable treatment for this condition. Note that surgery performed at this time carries a high anaesthetic and surgical risk due to the animal’s weakened condition. By the time a female dog is 10 years old, she has a 1 in 4 chance of developing this condition if she is not previously sterilized. Uterine and ovarian cancers are other conditions that can develop in the older undesexed female dog and cat. Sterilization removes these organs and the chance that the animal will develop these conditions.

Rabbits: Uterine adenocarcinoma is the most frequently diagnosed tumour in rabbits more than 3 years of age and has an incidence of 50 – 80% in certain breeds of rabbits. Metastatic disease from this tumour is slow to develop, but the prognosis for this disease is poor in rabbits if metastases have already occurred.

3) Preventing behavourial changes

Dogs and Cats: Some dogs and cats exhibit marked behavioural changes during the onset of oestrus. This is particularly marked in female cats who are wont to vocalise incessantly when they are on heat. Some dogs become more aggressive when on heat.

Rabbits: Intact female rabbits can be aggressive and territorial and when on heat, may exhibit nesting behaviour that involves ripping out large clumps of hair from their dewlap. Some rabbits may even go as far as tearing the skin on their dewlap open while on heat.


1) Preventing prostate enlargement

Enlargement of the prostate gland (prostatic hyperplasia) occurs in older male dogs and can result in pain on urination, straining to urinate as well as constipation. Early sterilization can remove the chance of this occurring in old age.

2) Eliminating Chances of Developing Testicular Abscesses and Cancer

Sterilization in male animals involves the removal of both testicles, thus negating your pet’s chances of developing testicular abscesses or testicular cancer.

3) Decreases Aggression Levels

Intact male animals are more likely to exhibit aggression if left intact due to increased testosterone levels. Sterilization reduces testosterone levels, which works to decrease aggression levels.

4) Decreases Urine Spraying

Urine spraying or urine marking is one of the most common reasons why owners choose to give up their pets. Urine spraying is markedly decreased in all male dogs, cats and rabbits after sterilization has been performed.

5) Decreases Humping Behaviour and Other Socially Awkward Situations

Socially embarrassing situations can be avoided by early sterilization, resulting in a decreased likelihood of your dog exhibiting humping behaviour. There is also a decrease in the amount of smegma production (the greenish-yellow liquid produced at the tip of the prepuce in male dogs) that would be likely to stain the floor.

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