As obligate carnivores, cats need:
Protein from meat or fish
Amino acids like taurine and arginine (from meat or fish)
Cats need much more protein in their diets than other animals. Kittens require one-and-a-half times more protein than puppies, and adult cats need two to three times the amount adult dogs require. The reason? While other mammal species use most of the protein they consume for growth and body maintenance, cats use it for this purpose plus as a source of energy.
In addition to their increased need for protein, cats have a higher requirement for amino acids found naturally in animal tissue, including taurine. Taurine is found in animal muscle meat, particularly in the heart and liver, and a deficiency causes serious health problems in cats, including cardiovascular disease and blindness.