Pete the Vet: When is the best age to neuter my pet, and why is it so important?

Thirty years ago, up to thirty thousand dogs were euthanised annually in Irish dog pounds just because they were surplus to requirements - vets and animal welfare groups tackled this by creating public information campaigns and a nationwide means-tested subsidised spay and neuter strategy by Dogs Trust

Pete the Vet: The cone of shame mightn't be an option for all dogs!

As Valentine’s Day approaches, love is in the air. While animals may not engage in the same type of romantic endeavours as humans, there is no doubt that their urge to find a mate and ultimately to reproduce are just as strong.

Spring is here, and the breeding season is revving up; most animals are seasonal breeders. For many mammals and birds, mating in mid-February leads to young being born (or hatching) from mid-March onwards. The timing means that the natural food supply, peaking in the summer months, fits the needs of the growing animals: first, the mother needs extra nutrition to allow her to feed her newborns, and the young creatures then need to be able to find plenty of food to allow them to grow and develop fat reserves by the time food becomes scarce in the autumn and winter.

In nature, the population of animals is regulated by the availability of food, water, shelter, and space, as well as the impact of disease and predators. It’s different for pets: humans ensure that they have plenty of resources to thrive, and we protect them to the best of our ability from disease and attacks by other animals. There is one serious negative downside to this: there’s a tendency for pets to reproduce too effectively and rapidly if we don’t take steps to control their fertility.

In the past, this has caused huge problems with overpopulation of dogs and cats in Ireland. Thirty years ago, up to thirty thousand dogs were euthanised annually in Irish dog pounds just because they were surplus to requirements. Vets and animal welfare groups tackled this by creating public information campaigns (such as www.spayaware.ie) and there was a nationwide means-tested subsidised spay and neuter strategy by Dogs Trust. It became “normal” to get dogs (and cats) spayed and neutered. The numbers of unwanted puppies (and kittens) fell as a result, and the number of dogs being destroyed every year reduced to less than two hundred in 2021. Statistics are not kept for cats.

It’s now widely accepted that spaying and neutering should be the natural choice for most pet owners. Apart from population control, it’s often better for the health of the individual animal.

The health benefits of spaying are well established. The obvious plusses are removing the risk of unwanted pregnancy, and halting the behavioural changes that happen when they come into season twice a year. It also dramatically reduces the risk of mammary cancer: The risk of a non-neutered female dog developing mammary tumours during her life drops from 70% to 0.5% if neutered before her first heat. Spaying eliminates the risk of pyometra (a womb infection), which occurs in 23% of intact females.. Importantly, there’s no evidence to suggest that allowing a bitch to have a litter of pups confers any health or behaviour benefits. This is an old myth that has long been disproved

Entire cats are seven times more likely to develop mammary cancer than those spayed when young. Mammary cancer is the third most common tumour in cats, and 80% of feline mammary tumors are malignant.

Castration removes the risk of testicular cancer which is one of the most common tumours in male dogs. Castration also significantly reduces the incidence of common non-cancerous conditions of the prostate gland e.g prostatic hyperplasia which otherwise affects 95% of dogs by 9 years of age. A number of other common issues (such as hernias and various other ‘under the tail’ problems) also happen less often in neutered males. It’s true that a smaller number of rarer issues actually happen more often in neutered males, but the balance definitely lands in favour of castration for health benefits.

The impact of castration on behaviour is more complex. The removal of testosterone from the body reduces some behaviours such as straying, territorial marking with urine and mounting behaviour (e.g cushions and people’s legs). Some types of aggression (e.g. dog to dog competitiveness) are reduced but not all types. It’s wrong to expect a dog to become quiet and passive after castration: this is a myth. Testosterone is needed to give a dog confidence and so it’s no longer recommended to castrate anxious or nervous male dogs as this may even make fear-based aggression worse.

In male cats, neutering reduces fighting and territorial behaviour by over 80%, which in turn reduces other issues such as cat bite abscesses, and the risk of Feline Immunodeficiency virus (FIV) Neutering also significantly reduces male cat urine marking behaviour.

The single most common problem caused by spaying and neutering is an increased tendency to obesity, but that’s something that can be dealt with by careful nutritional management. Mild urinary incontinence is more likely to occur in bitches but most cases respond well to simple treatment with daily medication in their food.

Advice on when to spay/neuter pets can vary, and it’s different for dogs and cats.

Both male and female cats should be neutered/spayed from four months of age.

Most male and female small dogs should be neutered/spayed at 5-6 months of age i.e. before a female dog’s first season. Both male and female large breed dogs should be spayed/neutered around 9 months of age, while giant breed dogs (such as Irish Wolfhounds) may be left entire till around 18 months of age, as doing the operations later has been found to reduce the risk of osteosarcoma in these breeds. It’s best to discuss the precise timing with your own vet, who knows your pet.

Our understanding of other possible impacts of removing sex hormones from pets is exponentially improving as researchers analyse big data extracted from vet clinics’ computerised animal records. So far, the message is clear: it’s better for most pets to be spayed or neutered.