Should GSP's be fed large breed dog food? Having worked with horses for many years, I am a firm believer that diet plays a huge roll in skeletal/joint health. So are GSP's considered large breeds/fast growers? In horses, you can tell that they're growing too fast when their legs get too straight. Is there a way to tell that a dog is growing too fast?

I'd say no. I hold my vet, my trainer/breeder, my GSP's breeder, and my AmBull trainer/breeder friends in high regard and all say, stay away from large breed food. I'd stick with regular puppy food (premium preferrably), the best you can afford and whichever one works for your dog.

IMO it's more important to make sure you don't over-exercise the growing pup, meaning no jogging or biking for miles and miles even if the pup is able and willing to pull along. The growth plates (soft ends of the bones that allow bones to elongate during growth) don't close until 8-12 months and are easily damaged by high-impact exercise (early spaying also affects bone growth during that time). No jogging etc. until 1 year old, no agility until 18 months old at least.

Thanks for that! I deffinetly agree about the limiting high-impact exercise. With my dachshund, we didn't spay her until after her first heat so that we knew she was mature. We did this upon recommendation since dachshunds are coinsidentally prone to back problems. Should this be done with GSP's too?