First let me say I have no personal experience with your breed. I own Boxers and they tend to stay lean up until about 3 years old. Lean is preferred over heavy.
Does he have loose stools or does he throw up from time to time? It is not uncommon for hooks not to show up in a fecal,most of the time the vet does a floatation fecal and they are less than effective,always ask for direct and floatation. I’ll get back with you as to another very accurate test for parasites.
Did you see his parents? Did their sizes meet breed standard? Was this pup a smaller than average pup in his litter?
Many times higher protein and a grain free food will make it difficult to put weight on a dog. Although overall I am not a fan of a LOT of grains,it seems that oats are easier than most digest and they add calories and can soothe the gut too.Do you give a good probiotic?
Alana makes nice foods, several people I have talked to lately are having success with Acana Regional Red (beef). I like Canine Caviar Free Spirit Holistique and First Mate chicken and blueberries. I don’t know if any of these are available locally in your area. Can you order from Chewy or PetFlow? They are fabulous
