Is it the vets duty to advise against?

In a way, yes, it is their duty... but only to a point (which is what I believe most do).

Because I chose not to get my pup spayed (no, I never plan to breed her, and I have never had any accidents while having unfixed females for most of my life) my newest vet keeps giving me all the warning of why i shouldn't think to breed my dog (mostly due to over population, but, keep in mind, I've never even suggested that I did want to breed her). I think my vet is trying to do the right thing by giving me the warnings.

But, I'm sure if a client/patient came in as a breeder with a pregnant dog then they still do what their job is...be a doctor. I'm sure doctors for pregnant (human) women face the same issues.

According to Yahoo Answers, most vets only advise on if the dog it "healthy enough to breed" not if it's ethical enough

Add (13 hours later): The only time I've seen my former vet give strong opinionated advice is when they're looking to make more money off you. "This Science Diet is the best food for your dog right now" Despite that it's nearly double the cost for that bag of corn.

I want and expect my medical professionals to be brutally honest.

Our vet has told me that she's been extremely vocal with clients who want to breed their dogs-- and I really appreciate that about her. A client wanted a letter saying that her dog was fit to be bred, and our vet refused-- and sent her home with info about dog overpopulation and BYBing.

I can't think of anything, within reason, that a vet could say to "overstep a boundary" with me. I want honesty and candor from someone who's supposed to be looking out for my dogs' best interests.

I think it is their duty to speak against breeding because owners might not know the health risks, or about genetic disease passed on to the litters.

I think overstepping would be pushing anything unnecessary like over vaccinating. But there's a fine line between informing and over stepping it's how it is said.

Did the vet advise against breeding your dog because it would be bad for her, or because he doubted your ability to choose a suitable sire and raise the litter properly?

If you have an out-of-control dog, any sane person would advise you not to expose children to it: dogs are carnivores, after all.

Veterinarians have consciences, too. If he offends you, take your business elsewhere.

Unless the vet determines that breeding your dog would be detrimental to the dog's health, I doubt that any would offer their opinion. And, while many vets may be well versed in certain breed standards, they are not experts in what it takes to win in the show ring or in the field - they're vets, not judges.

In addition, since most people would accept criticism, even constructive criticism of their dog as rude and unsolicited, the vet would likely lose many customers along the way.

So, "overstepping their boundaries" - No, everyone has an opinion - educated or not, we all have our opinions. But, in the case of someone whose bread and butter counts on return clients, it would be advise able to keep ones opinions to ones self.

ADD: I think the best examples of what I'm referring to can be seen on this forum every hour of everyday: People thinking that they have a dog that is worth breeding - never mind that it is a mutt, never mind that it is a terrible example of the breed standard. What some vets can do for those who indicate they are going to breed their dog, would be to give them an informational pamphlet that explains breeding and whelping thoroughly along with the pit falls, and also to provide them with some statistics on shelter animals and the euthanasia rates worldwide. They may take that as less of a personal affront and be more reasonable. Or, they may just walk out of that vets office - never to return - and breed their dog anyway.

ADD #2: @Lab-Rat Dingbat - that's my point exactly. Vet's aren't license to be "ethical" which is subjective at best. They are trained to take care of the health of pets - not to legislate ethics. Just like many vets (unless you have an excellent rapport and long-standing relationship) are reluctant or will even refuse to advise you to euthanize your pet, even when they know there is little to no means of saving him, the dog/pet is your property and the decision is your.

ADD#3: @Raw Rescue Pups: On a personal level, I agree with you. When I pose a question to my vet, I want the truth and, I do believe that my long-standing relationship with my vet helps promote that type of honesty. But you and I, and most people who respond in the D/S are among an extreme minority as far as dogs are concerned. Proof of that is in our overflowing shelters, the HIGH euthanize rates and the type of questions that we see on this forum every day. I believe that many many individuals would take offense at a vet telling them that their dog was healthy, but don't breed him/her since they're not breeding material, or because there are too many dogs in shelters. I think many people would be insulted and stop patronizing his service. I haven't bred and shown dogs in many years, but when I did, I NEVER asked my vet his opinion of any of my dogs breed worthiness or show potential. As far as showing went, I knew far more than he about my particular breed and he never offered any opinions on those subjects. In almost every instance, I deferred to his recommendations when it came to health issues, that was his expertise; but showing and breeding potential was mine. And, obviously, if someone has to ASK their vet if there dog is breed worthy, they should not be breeding. So, again, I definitely do not believe it is a vet's DUTY to tell anyone not to breed their dog for any reason other than health-related. He can, of course, offer his opinion, but from a business standpoint, he should tread lightly.

Your vet must be seeing something you don't, like your dog isn't breeding quality. They also know what happens to excess dogs.

You vet knows best... She would probably not keep a very good bloodline going OR if she is a mutt she shouldn't be bred