There has been much debate in recent years regarding the best age to spay or neuter our pets or should we sterilize them at all. This is due in large part to the findings of three major studies and the push in Europe to leave dogs intact.
The Hart Study (Golden Retriever Study) used a small number of Golden Retrievers and found that spaying/neutering resulted in an increased likelihood of some cancers. The Hoffman Study looked at 70,000 dogs and 185 breeds were represented. It was found that sterilized dogs had a decreased chance of dying from infectious, trauma, vascular or degenerative disease but an increased likelihood of suffering from cancer or immune mediated disease. The last study to look at the pros and cons of sterilization was form the Banfield Pet Hospital. It reported that neutered male dogs had an 18% longer life while spayed females lived 23% longer than their intact counterparts.
The results in cats were more dramatic with neutered males living 62% longer and spayed females lives were 39% longer. With so much information (often conflicting) how do owners decide when and even if to spay and neuter their pets? The best advice is to talk to your veterinarian and depending on your pet and it’s lifestyle you will be able to make an informed and appropriate decision.
Most questions regarding the age at which to spay or neuter your dog can be answered by looking at the size of your pet and its lifestyle/environment.
- Small breed female dogs will often mature early so we recommend spaying before 6 months of age which is often when they will experience their first heat cycle. *Unless the puppy has an active vaginitis the advantage to spaying before the first heat is an almost 0% chance of developing mammary tumors later in life. Although genetics also play a role in the development of many cancers, the link between heat cycles (estrogen) and mammary tumors is well founded and results in the above recommendation.
- Medium/large breed females: It is necessary to discuss the activity level of your dog and if there will be performance/agility plans in your dog’s future. Reproductive hormones are responsible for growth plate closure so spaying your female before sexual maturity can result in altered confirmations of some joints; the stifle joint the most worrisome. Unfortunately it can be difficult to predict if orthopedic/cancer issues are most important to your pet so be sure to talk with your veterinarian. Often we will spay closer to one year of age (or the second heat cycle) to allow these dogs to get as close as possible to sexual maturity.
- Small/medium breed male dogs: It is often recommended to allow males to reach sexual maturity (approximately 12 months of age) before neutering as there are no health advantages to neutering young. Behavioral issues will often become the determining factor regarding age at neutering as urine marking, roaming and aggressive behaviour between other dogs will be seen more frequently with intact males.
- Large/giant breed males: These dogs are usually purchased because of their appearance which is largely dependent on testosterone. This is why veterinarians will often delay neutering until after sexual maturity (1 to 2 years of age). It is also important to have reproductive hormones present for the normal closure of growth plates avoiding tall/lanky males and altered confirmation of hind limb joints (ie: stifle).
The discussion regarding cats is much simpler as population control and unwanted behaviors necessitate spaying and neutering before 6 months of age. Thousands of cats are euthanized every year due to overpopulation so please spay or neuter your cat.
Written by: Dr. Terri Chotowetz