 You'd never knowingly feed your dog sawdust, but it's one of the most common fillers found in dog food today. Even the ones labeled healthy can contain powdered cellulose, otherwise known as wood pulp. I'm veterinarian Dr. Marty Goldstein. Your dog needs a biologically appropriate diet. That's why I developed Nature's Blend. She developed an aggressive cancer. She was put on pain meds just to help cope. She was limping through life and got very, very dopey from the pain medication.