Michelle has an excellent point, that most pet owners are not responsible enough to own an intact dog. Too many will slip up once and end up with yet another "oops" litter.
Most of my dogs have been spayed females and they were all spayed at about 6 to 9 months of age. None of them had any problems as they got older but they all had a happy home life with little stress. Although from my recent reading, I would not spay a female again until she was two years old, or at least until after her first heat.
There are studies that show there is an affect on growth with early neutering, but I don't have the link at hand. It's something about the early neutering causes a loss of hormones which make the growth plates in the bones not close as soon as they should and the dogs grow taller and more lanky than they would if they were neutered at about two years of age.
I think there is also a correlation with female dogs and early spaying but I would need to go find the info. If anyone has those studies, please post them!
But I had found this article posted else where and thought it was interesting. It talks about cancer in spayed and neutered pets.
I find the article makes a point about the loss of the hormones from the spay and in a stressful situation, they seem to have found a link to cancer.
And I have read several of Milani's books, they were quite good. I did not know she had a web site but she does and the article is from there:
"Spay, Neuter, and Cancer: Revisiting and Old Trinity"
Perhaps no aspect of pet ownership in the U.S. elicits as passionately supportive emotions as the subject of spay and neuter. In fact, this orientation is so well established that saying anything that questions the procedure is akin to blasphemy. However, just as women were routinely relieved of their reproductive organs with a "La de da, you'll never miss 'em" attitude until studies exploring the nonreproductive effects of reproductive hormones made human physicians rethink this position, so veterinarians and other animal-care professionals are making tentative moves to rethink wholesale sterilization of companion animals, too.
To understand what difference this may make in our attitudes about the procedure, let's consider the subject of cancer. Most dog owners have heard that spay and neuter prevent testicular and mammary (breast) cancer: however is that the whole story relative to cancer or is there more to it?
Obviously, if we remove a dog's testicles, there's no way he'll develop testicular cancer. On the other hand, most dogs who develop testicular cancer respond well to castration, so the advantages of preventive surgery are perhaps not as great as one might expect. Although intact (unsterilized) females have a higher incidence of mammary cancer, the dog's weight plays an important role in the process: intact females who are lean at one year of age have a lower incidence of the disease compared to their chunky cohorts.
In an interesting article in the August Veterinary Practice News entitled "Can we neuter cancer in dogs?" veterinary oncologist Kevin Hahn opens by saying that, after reviewing studies reported over the last 30 years, he's not sure what to recommend to his clients. Like most veterinarians, Dr Hahn mentions the higher incidence of testicular and mammary cancer in intact animals, but also notes that spayed females have a 4 times greater risk of cardiac hemangiosarcomas, and neutered males also show a significant increased risk for this cancer compared to intact ones.
Another cancer Dr Hahn discusses that deserves mention is prostate cancer because a lot of people erroneously believe that castration prevents this. In reality, it does not. In fact, castrated dogs have up to a 4 times greater risk of developing prostate cancer than intact animals. At the same time, spayed or neutered dogs have a 1.5 to 3 times greater chance of developing bladder cancer. Because of this, rectal examinations and abdominal palpation should always be part of a routine veterinary physical examination.
The link between sterilization and osteosarcoma (i.e. bone cancer) is also troubling: Spayed and neutered animals are twice as likely to develop this cancer. Those spayed or castrated before their first birthdays had a roughly 1 in 4 lifetime risk for osteosarcoma and were significantly more likely to develop a tumor than intact dogs.
The article then goes on to discuss the role of hormones and genetic controls in cancer. All agree that there is a connection, but no one knows exactly what it is. However, in his article Dr Hahn discusses a study done by Dr David Felman (and published in the June Nature) that I find intriguing because of how it may relate to the role the animal's behavior and his/her relationship with the owner plays in cancer. In a very tiny nutshell, the study looked at two gene mutations that lead the stress hormones cortisol and cortisone to trigger the growth of later stage cancer cells.
Because cortisol is also one of the hormones that's elevated when stress results in animal behavioral problems which, in turn, may result from human-animal relationship ones, it would seem that avoiding such elevations of this hormone by treating bond and behavioral problems could conceivably lower the probability of cancer in some animals, or improve the survival chances of those already afflicted with the disease. Although such a hypothesis might seem to require too great a leap of credibility for those who associate cortisol and cortisone with those drugs that counter inflammation and itching, another effect of these hormones is that they undermine the immune response. So while they may benefit animals who encounter occasional stresses of brief duration, these same substances may seriously undermine the health of those who daily live in stressful environments. In that case, not only will these animals have a higher probability of developing stress-related behavioral and medical problems (such as aggression or separation anxiety displays, irritable bowel syndrome or chronic or recurring urinary tract conditions), these animals' taxed immune response may experience more difficulty recognizing and dispatching mutant cells before they multiply and form cancers.
Currently the exploration of the nonreproductive effects of sex hormones is in its infancy and, unlike the rise of feminism which challenged the philosophy underlying hysterectomy and ovariohysterectomy in women, many of those who normally claim to speak for the animals are usually quiet about how sterilization may affect companion animals. Like Dr Hahn, I, too, have reviewed the literature and am not sure what to tell clients. However, I do know that unless we can free the subject from the emotional cocoon that has protected spay and neuter from objective scrutiny all these years, our pets won't be able to benefit from the knowledge that is slowly, but surely, being generated on this subject.
And I see she's written a sequel to the article above:
"Reproductive Emotions and the Human-Companion Animal Bond"
Two months ago I wrote a commentary about spaying and neutering in which I quoted study results complied by one group that were misquoted by the author of another article. The legitimate confusion this generated as well as some of the highly emotional e-mails I received about that commentary has led me to think about the role emotions play in this issue. But first, the correction.
I wrote that dogs younger than a year who were spayed or castrated have about a one in four lifetime risk of developing bone cancer and are significantly more likely to develop this than intact animals. What the article I was using failed to note was that the study ("Endogenenous Gonadal Hormone Exposure and Bone Sarcoma Risk," Dawn M. Cooley et al. Cancer Epidemiology Biomarkers and Prevention, Vol. 11, 1434-1440, November 2002) was done on 71,004 rottweilers. Thus based on the study we can say that delaying spaying or castration until sexual maturity confers some protection against bone cancer in this breed, but we can't say anything about that relationship in any other breeds.
Now on to the responses I received about that commentary. To me, the first intriguing point regarding these was that none of the negative comments challenged the above unintentional misrepresentation of information. The one e-mail that did was very thoughtful and I immediately realized my error. Hence the above correction. That the negative e-mails did not address the data could have occurred for several reasons. One is that studies comparing intact and sterilized companion animal populations seem more likely to show up in obscure scientific journals than veterinary ones, even when the researchers are veterinarians.
The second reason why none of the negative e-mails I received challenged the scientific findings could be because scientific evidence is not an issue that warranted their writers' consideration. Instead of analyzing or even condemning the studies that I described, they took a purely emotion-driven kill-the-messenger approach.
One typical of this genre said that, even if I didn't mind living with male dogs who lift their legs on everything and females who bleed all over place, other people didn't want to live like that. At the same time as the mental image those naive comments elicited made me, Ms. Anal-Neat-As-a-Pin, chuckle, this and similar comments saddened me because these people obviously believe that their righteous indignation renders even the most basic knowledge of normal canine physiology and behavior unnecessary. Worse, they have so much energy tied up in their emotions demanding mandatory spay and neuter for all dogs and cats that there's none left for the difficult task of objectivity evaluating the science and ethics underlying this extremely complex subject.
The other reason these emotion-driven responses are so troubling takes us back to the fact that so few of the articles comparing intact and sterilized companion animals show up where you would expect them: in the veterinary, humane, or animal welfare literature. Logic says this occurs because these researchers don't submit their findings to those journals, or those journals won't publish them if the researchers do. When I ask myself why this would happen, one explanation that comes to mind is that neither the researchers nor the journal editors want to deal with the emotional fall-out, no matter how rigorous the research or beneficial the results for animals. Having had a mild sampling of that, I can understand this. On the other hand, I must ask myself how long we're going to keep using the image of unwanted puppies and kittens or fantasies regarding the disgusting behaviors of intact animals as a shield to protect ourselves from open and thoughtful examination of the effects of sterilization on the animal to whom it is done.
Thirty years ago, the lowest form of pet-owners were the person who got dogs or cats and bred them so their kids could see the miracle of birth. We now live in a society in which a child's first memory may be of the beloved family pet dying of or being euthanized for cancer or some other immune-mediated disease for which no cure is known. Frankly, I don't see that as a valid trade-off and certainly not one that will ensure a healthy companion animal population in the years to come. If there's some link between these and other diseases and spay and neuter, let's find out what it is. Then we can make a rational decision whether the price that all sterilized animals and their species are being asked to pay for the behavior of an irresponsible portion of human population is worth it.