Supplements are not necessary when a cat is being fed a complete and balanced food, unless specifically directed by a veterinarian.
- Milk is a food and not a substitute for water. As a food, milk is incomplete and does not provide a balanced diet. It can be useful as a treat for some cats, however, large quantities of milk may not be well tolerated. Milk contains lactose, which requires the enzyme lactase for breakdown in the intestinal tract. If the intestinal tract does not contain sufficient lactase, consumption of a high level of lactose can cause diarrhea in some pets.
- Repeatedly adding raw eggs to a cat's diet can cause a deficiency of the vitamin biotin. Raw egg whites contain avidin, an enzyme which ties up biotin (makes it unavailable for absorption into the body). Symptoms of biotin deficiency include dermatitis (inflammation of the skin), loss of hair, and poor growth.
- Some raw fish can cause a deficiency of the vitamin thiamine. Symptoms of a thiamine deficiency include anorexia (complete loss of appetite), abnormal posture, weakness, seizures, and even death. Repeatedly adding raw fish to the diet of a cat is not recommended.
- Table scraps will not provide the balanced diet which cats require. Ideally, table scraps should not be fed. Owners who do offer them should never feed more than 10 percent of the animal's daily food intake.
- Although cats may enjoy meat, it is not a balanced diet. Raw meats may contain parasites, and cooked meats can be high in fat and do not contain a proper balance of nutrients.
- Raw liver, fed daily in large quantities, can cause a vitamin A toxicity in cats. This is particularly true if it is fed along with a complete and balanced diet already containing ample vitamin A.
- Small soft bones (such as pork chop or chicken bones) should never be given to cats, as they may splinter and lodge in a pet's mouth or throat.