Find a vet

[Trev]

I don't usually bother with vets either, if a bird is sick it will either die or get better !!
As has already been said, observation is the most important tool we have. Whatever livestock you keep, if you can't spot a sick or weak one then you probably shouldn't be keeping livestock at all.
I did however once take a baby that had a badly injured eye to one of our local vets and he did remove the eye as it was beyond saving.
Many years ago I also took a pigeon, that had badly damaged a leg, to a local bird sanctuary, the vet there stitched the leg back in place and saved the bird from potentially losing it.
As for testing it's just something I've never done, but then again I'm not often at the top of the result either so make of that what you will
I don't lose many birds on the road though and do usually get them from the distance so must be doing something right, they just dont fly quick enough

[Murray]

I am like Trev and Andy. I never take a pigeon to a vet and almost never use any medication.
I think I have a small advantage in that I live in a great climate. It is warm for most of the year and mostly dry. The pigeons get large doses of the best medicine, sunshine.
In the last few years I have introduced some new bloodlines. Heremans and Jos Thone's mainly. They came from pigeons that have been regularly treated for canker, cocci etc. They had to develop their own immunity, because they don't get that here.
They all get some extras, garlic and cider vinegar, fresh chopped vegetables, a bit of fish oil, stuff like that. At present they are all living together in an old chook shed while we are between homes. I gave them a bath in there a couple of days ago and yesterday they looked and felt a million dollars.
Bouncing with health.
I did treat them all for canker once last year, some of the new pigeons had youngsters with a touch of it. A 5 day course of Emtryl. Cleaned them up. That's the only time my birds have had medicine in over 10 years.

[king]

It might not be the honesty of the seller - but if the birds are bred in an "open stock section" can you always guarantee the parentage of each pigeon bred each and every round?

Whilst your right you can't 100%. But do most hens let any cock tread them? I've yet to breed a YB of a colour that was impossible from the pair that hatched it? (FLOATED EGGS EXCLUDED) And if hens regularly let any cock tread them, fanciers wouldn't have a problem with clear eggs from older stock?
The majority of birds in an open section would only get the chance to tread in their own box. Every time I've see birds try to tread outside of their box one or more other cocks stop the cock treading by knocking him off.

[MIL]

Exactly, so the DNA just gives the buyer the absolute definitive clarity that the bloodlines that he was striving for is actually what he has acquired

I wouldn't have an issue getting a bird DNA'd myself.

[Murray]

This is quite correct. You cannot be assured that the youngsters have guaranteed parentage unless the parents were confined until after the second egg is laid. Many is the time I have seen a hen mate with a cock who most certainly is not 'er old man".
Never worried me much, I don't sell pigeons. And as has been said, you can absolutely tell if a red youngster turns up it had a red parent, if a pair of chequer pieds throw dark chequer pieds 100% of the time, it wont suddenly be a blue bar, or of course, two blue bars will have two blue bars in the nest.
I have a small stock shed, in pieces just now, with 4 nest boxes. And yes, I had two red cocks, a pair of blue bars and a pair of Chequer pieds in it.
They flew out every day, because all mine do, so I had no way of telling if mum was getting around a bit. But the youngsters seemed to be a good guide.