Since Morinville Vet Clinic acts as a holding facility for stray animals in an area north of Edmonton, the veterinarians and staff see lots of animals that are pregnant and homeless. We always try our best to find homes for all the offspring, but it would be so much better if the lost pets had been spayed or neutered in the first place.
Spaying and neutering are the procedures that veterinarians use to surgically sterilize female and male pets. In both procedures, the main sex organs of the pet are removed. The vets at Morinville Vet Clinic have considered a lot of research on the best age at which to do surgery on dogs. There is not much evidence of a benefit from delaying the surgery in cats, only risks.
The benefits of sterilizing an animal before maturity are that the surgery is faster and less painful because the organs are smaller. It also decreases the risk of mammary (breast) tumours later in life. Animal shelters typically sterilize all puppies and kittens to avoid adding to pet overpopulation, and often will do this surgery at two to three months.
The benefits of delaying surgery until maturity have been shown in a number of different studies. Most of these relate to the effects of altering the levels of sex hormones: estrogen, progesterone and testosterone. Changing these hormones has been shown to change how some body systems develop. One main consideration is that leg bones continue to grow longer if a dog has surgery before full maturity. This excessive lengthening leads to an increased risk of joint problems, especially in the hips and stifles. This is one of the main reasons why larger breeds are recommended to have their surgery after they are a year old and have reached maturity.
There are certain other systems that seem to be affected by the hormone changes that come with surgery before maturity. The thyroid gland is certainly affected by changes in hormones. Dogs that are sterilized before maturity have tripled the risk of having low thyroid hormone than those who are sterilized after a year of age.
One of the biggest risks of early surgery to come out of the studies was the chance of certain cancers in large breed dogs. The most important of these are hemangiosarcoma (a tumour of the spleen, liver or heart) and osteosarcoma (a tumour of the bone). Both of these cancers are very aggressive and almost certainly fatal. Sterilizing early doubles the risk of osteosarcoma and triples the risk of hemangiosarcoma. The research that measured these risks was done by looking at a lot of cases over a period of many years.
In the end, it is up to the pet owner when they wish to have their pets spayed and neutered. That is a decision made for a lot of different reasons. From a medical standpoint, Morinville Vet Clinic recommends that all dogs that will grow to more than 27 kg (60 pounds) when they are adult should have their surgery at one year of age, and cats and smaller dogs should have their surgery at six months.
Written by Morinville Veterinary Clinic