My 8 year old Lab has occasionally had bouts of GI distress accompanied by bloody mucous diarrhea. Our vet last year felt it was something he ate and put him on a chicken and boiled rice diet. It is back again and has been going on for the last several weeks with incidents every 2 or 3 days. It usually occurs in the middle of the night when he goes out several times, each time pacing the yard and sometimes eating grass (on occasional he will vomit). He ultimately has diarrhea with the final bowel movement being blood filled mucous. He isn't real hungry in the morning, but eats and everything and seems fine. The rest of the time his bowel movements are normal and there doesn't seem to anything wrong. He is eating a higher quality commercial brand diet for many years. Can you suggest next steps other than lots of testing?
Dietary hypersensitivity would be a consideration to explore prior to additional tests. A grain free limited ingredient diet trial is suggested. Natural Balance Sweet Potato & Bison or Venison or EVO Herring & Salmon may be obtained at larger pet stores and many boutique pet food stores. With a diet trial, nothing else can be given (no table food, raw hide chews, etc.). It this does not resolve the problem then discuss with your veterinarian a referral to a specialist for further evaluation as chronic enteropathy (inflammatory bowel disease) or other intestinal disorders would likely be present.