Any thoughts on giving a growing pup a joint supplement for support? Yes...no? If yes, what do you give and at what age do you start giving it? TIA

JMHO....I've tried all sorts of things for myself, dogs and horses with no marked improvement and/or prevention capabiities. IMHO....use glaucosamine if you like, keep their weight down, feed them good food, try to limit injuries (stuff happens) & hope for the best (and try NOT to worry about what ifs down the road).

I use it only on seniors or dogs with issues. I don't ever give to pups. It's like pouring it down the drain, IMHO

I use Glyco Flex Classic for pups.

I have been using Glycoflex for 20 years. From weaning till old age. They just take the regular glycoflex. If they have issues when older they have Glycflex II and III with larger doses for pain. It is made by Vetriscience.

I don't believe in giving supplements to growing puppies and I'm one of those who believe in letting a puppy be a puppy. I also do not believe in keeping them thin. Why? Because if they are going to have joint problems, I want to know. I don't want to coddle the dog, hold their growth back or otherwise cover up a potential genetic problem. If my dogs get through puppyhood by getting plenty of exercise and play, keeping a healthy weight, growing to their fullest potential, and without supplements and xray clear, then I know my lines have strong joints.

I'm sorry, I have to take issue with this last post. Drs. Wind and Morgan, from UC Davis, did research several years ago regarding joint disease in puppies, and they found that the period from 4-6 months is a critical period developmentally. This means that any injury to the joint during this critical period can cause permanent injury. Just like the fear imprinting period from 8-10 weeks (some say 7-11 weeks) is a critical period in which fearful, painful or extremely stressful experiences can have permanent consequences in the emotional and personality development of the puppy.
We do not let human children run marathons or pitch an entire baseball game, they do not allow fillies and colts younger than a certain age to race, and puppies should not be encouraged to play rough on hard surfaces, jump out of cars or pickup trucks, play frisbee or retrieve a ball repeatedly. An orthopedic surgeon told me once that the worst thing you can do for a dog orthopedically is to throw the ball, especially puppies.
A "healthy weight" is also very subjective. I know somone who was feeding y cups of puppy food a day (the puppy was obese), letting the puppy jump out of her vehicle repeatedly and keeping him on concrete who voiced this same sentiment as you and that puppy was the only one in the litter with elbow dysplasia at 6 months.
I personally don't go crazy with supplements or keeping a dog super thin, but I believe caution is in order, especially in the 4-6 month critical period. Exercise and play, yes, but allowing the puppy to go crazy with other adult dogs and get repeated trauma to the joints, no.

And I said nothing of the sorts of letting a puppy do anything of the non puppy things you mention (running marathons=forced exercise, jumping off of high surfaces, being obese, etc). I merely stated that I let my pups be pups and play/exercise as they wish, keeping them at a weight that will not hold back growth, etc. I do this because I want to know that my dogs will be dogs without having to go above and beyond to coddle them so they will not be lame and pass x-rays. It has worked well for me over the years. The few dogs that have had problems were from lines where there were known problems that cropped up from time to time. I found a problem and I placed those dogs in pet homes. They made fine pets, and weren't used for breeding because they had genetically weak joints.

I do have stairs that my young dogs climb. I've even had them do silly things on walks. I've never had them injure themselves by being silly or playing too roughly. If a dog is going to have good joints, they will have good joints. This is what I want to know and I will stress my pups just that little extra bit by letting them do puppy stuff. As I said, if they x-ray normal(and most do), I know I have a very sound line.

Blaming bad joints on the possibility of the pup being too heavy, allowed to jump off high areas or playing roughly is just a breeder in denile that they have joint problems in their line.