Proteins and Essential Amino Acids

Proteins, like carbohydrates and fats, are made up of carbon, hydrogen, and oxygen. In addition, proteins contain nitrogen, and many contain sulfur. Amino acids are the basic building blocks of protein. Proteins can range in size from a few amino acids, to a substantial, complex matrix of amino acids that are intricately folded.


Protein plays an important role in all functions within the body. They play key structural roles in hair, feathers, cartilage, and cell and tissue walls. They are important for transporting other molecules throughout the body. They regulate muscle movement. They play a crucial role in digestion and absorption of nutrients. They make up the antibodies in the immune system. These reasons, plus so many others is why high quality protein is vital for optimal health of pets. The body has the ability to break down proteins into their individual amino acids and build what it requires. As a result, it is more proper to state that the body has an amino acid requirement, rather than a protein requirement.


There are 22 amino acids required for cats and dogs. The body of an animal can create certain amino acids from basic building blocks. Others need to be obtained from the diet. The ones that must be ingested are referred to as “essential amino acids.” There are 10 essential amino acids in dogs, and 11 in cats. The list is the same for both species, with the addition of Taurine as an essential AA in cats.  Taurine is nonessential in dogs as they can synthesize their own. 

The list is as follows:

  1. Methionine

    • Typically the first limiting amino acids. It is important as it is used to synthesize other amino acids, cysteine (dogs and cats) and taurine (dogs). In cats it is also used to synthesize another amino acid, felinine.

  2. Tryptophan

  3. Histidine

  4. Leucine

  5. Isoleucine

  6. Theronine

  7. Phenylalanine

  8. Argenine

  9. Valine

  10. Lysine

  11. Taurine (cats only)

    • Can be synthesized by dogs using methionine and cysteine. Cannot be synthesized by cats.  It is important for eye and heart health, reproduction and metabolism.