Pet Care 101: When should I desex my pet?

There has been much debate between pet owners and veterinarians alike about what age is the ‘best’ age to neuter a dog or cat. Unfortunately the evidence is not black and white, but instead 50 shades of grey. I recommend neutering at 6 months of age for most of my cat and dog patients, and here is why! 

Neutering under 4 months of age

Advantages:

·         Simple surgery with reduced risk of haemorrhage (bleeding)

·         Prevents unwanted pregnancy

·         Animals can be rehomed already neutered, ensuring they will not procreate and add to an already overwhelmed population of strays and abandoned pets

Disadvantages:

·         One study showed there was increased risk of infection after surgery in pets younger than 12 weeks old

·         Anaesthetic safety reduces in very young animals

·         Depending on the study there has been a 4-20% increased risk of urinary incontinence in female dogs desexed under the age of 3-4 months

Neutering between 4-12 months of age:

Advantages:

·         No evidence that there is an effect on incontinence levels

·         Surgery is still simple, with small reproductive organs

·         Increased anaesthetic safety

Disadvantages:

·         Female dogs are 9% more likely to develop mammary (breast) cancer if they have been on heat once (generally first heat is after 8 months of age)

-      Cats can fall pregnant from 6 months of age, depending on when they reach sexual maturity sometimes even younger. It is very important to monitor female cats for signs of being on 'heat' to prevent an unplanned pregnancy.

Neutering after 12 months of age:

This kitten was brought to me barely able to move, after falling pregnant at 8 months of age and having trouble birthing. Unfortunately all of her kittens where dead, and has caused a serious infection in her body. But with surgery to remove her infected uterus, antibiotics and some TLC the mumma-kitten did recover.

 Advantages:

·         Female dogs who are not desexed have a 15% chance of developing a pyometra (infected uterus which is life threatening) by the age of 4. Cats do not develop pyometra as commonly but the risk is still there.

·         Eliminates risk of reproductive organ cancer

-      Entire cats are more likely to contract Feline Immunodeficiency Virus (FIV) through cat fights and mating

·         Allows longer for development with oestrogen/testosterone which some studies show reduces risk of obesity and some other diseases (however these diseases are not common)

Disadvantages:

·         Female dogs are 26% more likely to develop mammary (breast) cancer if they have had two heat cycles. Both male and female cat's are more likely to develop mammary cancer if they are not neutered.

·         Surgery can become more complicated, especially in females, as the uterus is larger with a greater blood supply

·         One study demonstrated an increase in surgical complications in female dogs over 2 years of age. 

Behavioural effects of neutering

The jury is still out on how much neutering influences behavior. One study showed a 25% reduction in urine marking, mounting and other ‘masculine’ behaviours in male dogs neutered before 10 months of age. A similar study showed a reduction in aggression in neutered male dogs, but the age of neutering did not have an effect. The results also suggested that neutering an already aggressive dog can help reduce the level of aggression. The results for female dogs are mixed, and potentially biased (focusing on certain species), but have shown both an increase and decrease in adverse behaviours in neutered females.

Male cats also show a significant reduction in urine marking behaviour when desexed before 12 months of age. Neutering does not seem to have a major affect on long term female cat behaviour, but if you have ever seen a female cat on heat it is not something you want to live through!!! (Imagine screaming all night, constant buttocks in your face and weird behaviours like dragging themselves across the floor by the front legs as if they were paralyzed...)

My final thoughts

Based on the pros and cons of each age group I recommend neutering dogs and cats at 6 months of age. I believe neutering at this age has the greatest number of benefits including reduced risk of incontinence, low risk of pregnancy, reduced risk of cancer (and other hormone related diseases) and an increased safety margin for surgery and anaesthesia. I recommend neutering ALL non-breeding dogs or cats, the diseases and risks associated with being ‘entire’ (not neutered) are just too great to ignore (including prostate and mammary cancer, pyometra, unplanned pregnancy and behavioural issues such as pets escaping because of their sex drive!).

 It is important for you and your veterinarian to make the best choice for your furry friend, but I hope this helps guide you and taught you a little more about the reasons many veterinarians recommend neutering at this age.

May all your tails be happy,

Dr Sheridan