At What Age Should I Spay

Or Neuter My Dog or Cat?


Ron Hines DVM PhD

There are allot of conflicting recommendations as to the best age to spay or neuter your pet. Traditionally, veterinarians suggested that dogs be neutered at six months of age. In the majority of dogs, this precedes the first heat cycle in females and the onset of male dog behavior ( lifting their leg to pee, showing of sexual interest, roaming, aggression). Smaller breeds of dogs tend to mature a bit faster than larger breeds so many toy and miniature breeds were spayed at five months of age.
Female cats reach sexual mature more rapidly than most dogs. I have found that once a female cat weighs 4.5 pounds, it is often fertile; and it usually becomes pregnant on its first estrus (heat) cycle. Males cats mature more slowly and when they do breed, it is usually someone else's pet that becomes pregnant. If your male cat has begun to spray urine in the house, it is time to get him fixed. However, many male cats never spray. Un-neutered male cats should never be allowed out-of-doors unsupervised. If they are simply shown the door, they will invariably get into fights with more dominant Tomcats and become injured.
American Heartland families would often allow their new pet to have one litter so the pet or the family's children could experience the "miracle of birth".
As humane organizations and animal shelters became more common and powerful, popular recommendations changed. Shelters and animal rights advocates are opposed to the indiscriminate breeding of pets. They have good reason for this - the more unwanted puppies and kittens that are born, the more difficulty these groups have in finding homes for them and the more likely it is that these youngsters must be "put down"(killed). Many shelters are so adamantly opposed to this, that they have strict bylaws or rules that no un-neutered pets can be adopted. That is why they favor early spaying. They also know that if a pet they have adopted out is not neutered in it's first 8 months, it is unlikely to ever be neutered. So, for them, this is a social, not a medical, issue. I know of no medical or behavioral reason to neuter a pet before its estrogen or testosterone levels begin to rise. By definition,this does not occur, in immature animals.
Some veterinarians prefer to neuter very young pets because their ovaries or testes (testicles) are still quite small. In this condition, there are less blood vessels that need to be tied off (ligated, sutured) so the risk of bleeding is much less. On rare occasions, female pets have died do to loss of blood when surgery did not go as planned. In very infantile (young) puppies and kitten, no suture need be used internally, instead all internal incisions are made with an electric knife called a cautery.
Veterinarians also appreciate that healthy, immature animals heal and rebound sorapidly after surgery. There are also economic incentives to neutering pets at a very young age.
Neutering pets was never part of God's design or Plan. We do it to ameliorate problems that we and these animals experience as humans adapt Nature to their own desires.
It is my personal opinion that estrogen, testosterone and other chemicals, secreted or influenced by the ovaries and testes (testicles), are quite important in the normal, healthy, development of dogs and cats. These hormones affect everything from brain and bone development to the percentage of fat in the body. There are likely many other lingering hormonal influences on the body that we do not yet understand. Because of this, I do not suggest that dogs or cats be spay at a very young age.
I have examined a great many puppies and kittens. I have never seen an instance where I felt that a puppy or kitten needed to be neutered before sexual maturity was imminent. I developed a way to decide the best time to neuter pets - I am sure many veterinarians made the same observations. Just before a pet reaches sexual maturity, permanent, upper canine teeth (fangs) replaced the ones they had as puppies or kittens. When these permanent teeth first erupt, every pet I have ever examined was still immature and showed no sexual traits. But very soon after these new teeth reached their final length, sex hormones begin to rise. That is when I set an upcoming appointment to spay the pet within 14 days. If, for some reason, you can not have the surgery in female pets, securely confine your pet and allow it to complete it's first heat cycle before scheduling the surgery. This surgery can be done during estrus (their period) but it becomes a much more serious operation and the crash in hormones must be quite uncomfortable.
Decisions based on hormonal analysis of the blood of your pet might be more scientific. But I have observed through many years of practice that examination of the canine teeth is quite accurate and effective.
Waiting too long to spay your pet is also not a good idea. After dogs mature, they often deposit abdominal fat that increases the difficulty of the surgery. Waiting too long can also lead to your veterinarian into having to spay a pregnant pet. Also, the tendency of older female dogs to develop breast tumors increase a function of age at spaying. (Please see Threads below)
Source: All Creature Care