If you need to test unique foods, I would test the urine. You may and should go gradual--have just a percentage of the food non-prescription and test the urine. The urine strip assessments can offer a warning signal if the new food isn't Doing the job out. Study the label: https://laneblvfp.blogscribble.com/37937195/getting-my-dog-food-royal-canin-puppy-to-work