What were the results of his latest annual vet exam? How long ago? Labs within normal limits? Does the dog have a diagnosis regarding gastrointestinal problems?
What did the vet advise?
“but I’m certainly not opposed to another medical check-up. We have a bag of Science Diet Gastro that the vet gave us when we have issues and he does well on it, but I doubt that’s a long-term food”
Some dogs do stay on a prescription food for the rest of their lives.
I would defer to your vet, after all, no one here has examined your dog.
At age 5 a large breed is close to being a senior. Please go see your vet. Further diagnostic testing may be indicated.
