Nutrients are divided into subcategories: protein, carbohydrates, fats, vitamins and minerals, and water.
Common cat food protein sources include meat, poultry, fish, and some plant ingredients such as corn gluten and soybean meal.
Protein is best known for supplying amino acids, or protein subunits, to build hair, skin, nails, muscles, tendons, ligaments, and cartilage.
Cats, best fed as true carnivores, require essential amino acids. One of these, taurine is not found in plant protein sources such as soybean meal.