Hello,Customer and thank you so much for your question this morning. Happy Easter!
It sounds like your Weimaraner is exhibiting classic signs of chronic, episodic colitis, or inflammation of the colon. It sounds like you have probably talked to your vet about this based on the treatments you have tried.
Colitis can have MANY possible causes and it can be frustrating to find the exact cause. I am glad to hear that your dog has been healthy in spite of this. Clearly based on the stool changes and the gurgling stomach your dog does have a tendency for upset gut. You have tried a lot of good ideas, with the diet changes, yogurt, etc. However, if this has not resolved the problem, further diagnostic investigating would be in order to see if a cause can be found.
This article has lots of detailed information on colitis:
A fecal exam and blood testing would be a good place to start with your dog. If your dog has not had a broad-spectrum dewormer, this should also be done. Routine dewormers may not eliminate all the parasites that can cause colitis, so using a special dewormer is always a good idea in these cases.
Given your dog's history, I am most suspicious of what we refer to as "inflammatory bowel disease", which is a chronic, immune system type disorder common in dogs. This is similar to Crohn's disease in people. There can be allergic components to this as well. Some of these dogs need regular therapy with antibiotics or anti-inflammatories, or other supplements to help control the diarrhea, such as probiotics (yogurt is one type of probiotic).
Here is some more information on IBD:
I hope this information is helpful and gives you a good starting point in investigating this further.
Again, have a happy Easter!
Dr. Marcia :)