Large and "giant" dogs such as Mastiffs, Sheepdogs or Shepherds, need to have a comfortable dog bed to rest and sleep in because they tend to have more joint problems than smaller dogs. (And, of course, a larger dog like me tends to destroy my owner's furniture more than a smaller pet.) Orthopedic dog beds are a must have for that large dog that has hip dysplasia or athritis.
Large dog breeds also have to have more exercise and eat healthier as they grow so quickly and their bones need to be able to withstand their fast weight gain as puppies. They also need to be well trained as their sheer brute force will cause even the most strong owner to be dragged along at the end of a leash. If you are looking for a large breed puppy, please only deal with reputable breeders. (Look on my links page for some reputable breeders or check out this website: http://www.hsus.org/web-files/PDF/Good_breeder.pdf.) Or if you are looking for an adult large breed dog, check into legitimate rescue organizations. If you are not worried about having a pedigreed dog but only want a mutt like me (I'm Shepherd, Boxer and Lab mix), still make sure the person or organization you are getting it from is reputable.
Please check out the websites on my links page for helpful topics and information on large dog breeds and good nutritional foods so your large breed dog stays healthy.