Couple of interesting articles in Dog World about early neutering.

Sorry - they're quite long! Neither are really pro or con, just examines the known effects of early neutering. If you have time to read them, they're quite interesting.

1) A Vet's View - Are There Any Pros To Early Neutering? by Prof. Steve Dean MRCVS

"At the recent British Small Animal Veterinary Congress one of the contentious issues was the subject of early neutering. Neutering dogs (and cats) at an early age, often as early as three to four months old, has become increasingly popular. However, several concerns have been raised about the potential ill effects arising from neutering a dog before it is mature. A recent effort to review the incidence of urinary incontinence, often thought to be more common in the spayed bitch, failed to prove a link with neutering despite finding plenty of published information but equally, the review, failed to dispel the theory either.
An RSPCA vet made a good case for neutering rescue dogs at an early stage. His argument was straightforward – because a charity often has only one opportunity to intervene and influence a dog’s future life, it makes sense to act when the dog is in their care. Evidently, many of their rehomed dogs do not return for further treatment and even if the new owner leaves with a voucher for neutering at a later stage they often do not use it.
Less impressive was the constant reference to lower cost being a significant reason for early neutering. It would be more digestible to hear a charity would be concerned to choose the time to neuter in the best interests of the dog and not because it improved the balance sheet. Nevertheless, it is worth noting that the RSPCA deals largely with dog owners who are the least likely to consult a vet or take a responsible attitude to an unwanted pregnancy. Thus this does influence their attitude towards early neutering schemes.
By way of contrast, it was refreshing to hear that the RSPCA recognises there is a lack of data to support early neutering. However, the charity still argues for early neutering mainly believing this contributes to reducing the stray or abandoned dog population. A further justification for early neutering is a lower likelihood of surgical complications in a young bitch. All this may be sensible for the rescue dog, but is this a sensible justification for the general practitioner to use?
The concept that neutering reduces the number of dogs requiring rehoming was strongly challenged by an Australian veterinary surgeon. She was a strong advocate of better education about dogs and their care. Her reasoning suggested how neutering was used more for the convenience of the owner and its intent is to make the dog more acceptable to live with. However it appears there may be an argument for not neutering based upon its affects on canine behaviour.
Assuming the public has unreasonable expectations of the relationship with their dog, surveys have revealed how poor behaviour is cited as a major reason for rehoming or euthanasia. In particular, barking and boisterousness are major reasons quoted for parting with a dog. Since most puppies often do both extremely well this is worrying. Furthermore, the public has a poor understanding of characteristic breed behaviour.
The genetic basis of behaviour is well established. However, in terms of neutering, removal of the reproductive organs at an early stage may coincide with a period of development when a maturing puppy is highly socially sensitive. Such periods are associated with changes in mental chemistry and it was argued this is not the right time to neuter and thus derange the normal hormonal changes expected around this time.
Veterinary surgeons often recommend neutering for aggression yet only about a third of aggressive dogs respond positively. Add to this the probability of greater cognitive impairment in older neutered dogs and this raises the question of why neuter dogs at all? This alone could be considered controversial yet a cancer specialist went on to state how early neutering in some breeds could increase the risk of bone cancer.
It is well known that early neutering delays the closure of growth plates in the long bones and in large breeds, already prone to developing osteosarcoma, this increased period of growth may double or triple the risk of bone cancer development. Further evidence suggests an increase in prostatic adenocarcinomas associated with early castration. In bitches it is generally accepted that neutering reduces the incidence of mammary cancer but in neutered bitches mammary tumours are more likely to be malignant.
The big surprise, however, was the revelation relating to the assumed benefit of early neutering in respect of the reduction in mammary cancer. It apparently is based on some dubious science. Vets have been educated to believe that spaying a bitch before her first season produces a dramatic reduction in the incidence of mammary tumours but it appears the data supporting this is very weak.
The last of the quartet of veterinary speakers dealt with incontinence, which is frequently associated with neutered bitches. It is however difficult to prove this link whereas obesity has a much clearer association. Lack of development of the vulva is also associated with neutered bitches but this expert’s view was obesity was more significant here, too. However, the accepted association between spaying and obesity does have to be taken account of.
Yet one issue was clear. Where an individual bitch suffers from juvenile vaginitis, it is more difficult to resolve if the bitch is neutered before her first season. In contrast it is worth noting how the condition often resolves if the affected bitch has a season. A case was made therefore for at least delaying the neutering of high risk breeds or dogs with specific diseases? Those breeds that suffer a high incidence of bone cancer are clearly logical candidates and indeed in some breeds it may be better not to neuter at all.
Returning to mammary cancer, the oncologist confirmed how little we know about the true incidence in entire bitches but added evidence to suggest removal of small growths at an early stage significantly reduces the risk of these tumours becoming malignant. Thus suggesting a timely, early surgical removal of small mammary tumours could be as effective as routine early neutering
Even in male dogs, in the lower urinary tract, transitional cell carcinoma is more common in neutered males and prostatic cancer, which is also seen in castrated dogs, is not currently a survivable cancer. At the end of the debate there was growing support for a more considered approach to neutering although nearly everybody understood why rescue dogs might be neutered routinely. However, even here, there are arguments that suggest public education might be more effective in reducing the numbers of unwanted dogs."

2) The RSPCA’s decision to early neuter by Geraldine Cove-Print

"We return to the subject of neutering this week, there has been quite a reaction to the information that the RSPCA, among others, now routinely neuter at before 16 weeks of age and often as early as six weeks.
I am grateful to Mary Price of the Severnvale Irish Setters who dropped me an email with her thoughts, she says, "One of the most tiresome consequences of puppies neutered very young is the early onset of urinary incontinence. In house pets the smell easily becomes offensive, and carpets, rugs etc on which the animal lies also begin to smell.
"There does not seem to be any cure for this, and I have never heard of vets warning of this. Although puppies neutered very young may initially elongate their bones, and appear skinny, adults put on weight easily, and it can be very difficult to avoid obesity, especially in breeds inclined to greediness. Their whole outlook can be coloured by a desire to find food, or something they consider edible.
"I have a small kennel of Irish setters, and the comment I get most when out with my dogs is, "Oh, what beautiful coats.” Very few vets either know or care that neutering an Irish (and some other breeds as well) affects the coat to an enormous degree. The shine goes and woolly undercoat predominates, they can then be very hard to groom, the coat does not repel rain etc, and they can get dense matts anywhere the coat rubs. This is very disappointing for the owner who fell for their beauty, and now has a fat smelly, woolly dog!”
Prepubertal neutering most certainly has some side effects that should be weighed up against the positive action of making that dog unable to breed. I visited David Yates, Director of the RSPCA’s Greater Manchester Animal Hospital to talk to him about the policy. He explained to me that the vast majority of the clients that used the RSPCA’s free clinics are unable to cope with an unplanned litter and that most of the dogs they see are often unvaccinated, poorly wormed and their general care is often less than adequate.
Unlike somebody who would use their vet for check-ups and routine health care most of the RSPCA clients will only use the hospital in an emergency, getting a client to return for a second visit is often hard work.
The young puppies that David sees, he knows, are likely to be sold to the same sort of environment as they have been bred in.
The RSPCA took the decision to neuter early in a dog’s life to make an impact on the number of unwanted and unplanned litters. He recognises that there are some downsides, the risk of osteosarcoma (bone cancer) is increased, there are bone plate changes but those risks are swamped by the overriding need to control the unwanted dog population in the UK.
I was particularly concerned about the consequences to large and giant breeds and asked David if the potential size of the dog would affect his decision to early neuter, he replied that he may delay the neuter but it would still be before puberty.
Vicky Collins-Nattrass of the Kezia Bulldogs has worked for many years as the volunteer co-ordinator for Bulldog rescue, she also wrote Bulldog Breeding for Beginners, the much acclaimed handbook for the breed. Vicky says that from her observations of many pet neutered dogs seen in rescue, the lean tall male Bulldog is typical of the neutered early type.
Vicky says, "I’ve seen this many times and lots come in rescue looking this way. Your column was the first time I’ve seen anyone acknowledge the facts. We are regularly advising people to neuter only after 18 months and preferably at three years (unless there a medical reason), to enable them to reach their maximum potential.
"We also think that the rush to neuter by vets is really to control the unwanted dog population understandably so, but are not expecting someone’s prized Bulldog to be roaming around the streets looking for a bitch so we cannot understand the rush in that case. Also Bulldog males who retain a testicle have a bigger risk from anesthetic before one year than they do of testicular cancer, the welfare of the individual dog is paramount.”
How many vets are willing and/or able to perform early neutering on puppies? David Yates told me that a list of over 500 vets were available for operations on kittens but that it seemed that prepubertal neutering of dogs is pretty much restricted to the main animal shelters.
We also discussed the need for a further long-term study to monitor the effects of early neutering, I do hope that this can be started soon as so much of the information gathered so far is from the US and much of it is either biased or contradictory.
The full interview is available as a Podcast; I do hope you find time to listen. David Yates clearly sees the disadvantaged and those less able to cope with veterinary bills at his clinic but mis-mates between dogs and the consequences happen in every echelon of society. I’d like to share an advert that appeared in a West Sussex forum online, the title was "Where is Saffy? Humphrey the black Labrador may be the father of her puppies! They met at Brandy Hole Copse, Saturday lunch time (I think it was April 21) and were stuck for about 20 minutes post-coitus.
"Unfortunately owing to the slight embarrassment of waiting for the dogs to separate I forgot to ask for the owner’s telephone number. He asked about Humphrey’s breed (Black Labrador, 5 years with Kennel Club pedigree)
"Saffy was a small, energetic and very friendly Chocolate Spaniel, two years old, and in season.
"I am the owner of Humphrey and would really appreciate finding a way to contact the family that own Saffy.” I’m not sure whether to laugh or cry!"

Hey,
I am Not sure at ALL????
What should I do???
I can't make my mind up as weather to neuter this beautiful boy of mine????
He is Three months and I just don't know???
How old should he be if i decide to do this??
Thanks Meliss
One of the most difficult decisions in the world

It's up to you in the end, but i personally do not neuter, they gain nothing from and it actually raises the risk of alot of health problems. Also does nothing for behaviour!

I have had Girls and I will always neuter, the choice really is yours on this one Xx

I think you have to weigh the pros & cons and make the best decision you can. If you're going to neuter I would advise waiting until your boy is mature (at least 18 months, preferably 2 years or more) so that he has a chance to be mentally & physically mature.

I had Saxon neutered at 6 months of age and has suffered no ill effects. He is now a year and a half (20 months) he is a healthy weight for his height and does really well in weight pull. He is the healthiest dog I know (other than a few perfectly manageable allergies) and his temperament is rock solid, he has never met a stranger (human or animal). I would neuter him again if I had the choice to make again.