A. It is important to remember that no single ingredient is the most important in a pet food. It can be challenging to assess and compare pet foods because there are so many available. Some brands on the market hyper-focus on the first ingredient, or even the first 4-5 ingredients. While these do represent the highest percentage of the formula by weight, a dog or cat would not survive or be healthy on just those first 5 ingredients. In fact, it is the combination of ingredients which contribute to the total nutrient profile and quality of a food. It is critical to understand that protein alone does not provide all of the necessary nutrients for dogs and cats.