I recently purchases #2014 Harlan Teklad lab blocks from "The Rat Shop." I've been feeding them to my rats now for a few weeks with their regular diet. Suddenly, the four rats of mine that have never had tumors before in their lives now all have tumors in the same spot and about the same size at the same time. The tumor is on their right side next to or right below their hind leg. Coincidence? I think not. I know they are tumors because I've been through them a lot before. Dora's is actually purple which I can see because of her hair loss. Our vet who has removed many other of my rats tumor says they are purple. This is lovely. Age might be a factor but I am highly suspicious of this food. Its not ever being fed to my rats again. Not with this experience.