Kittens require a high-calorie diet that contains more protein than the diet of adult cats. Young orphaned kittens require cat milk every two to four hours, and they need physical stimulation to defecate and urinate. Cat milk replacement is manufactured to feed to young kittens, because cow's milk does not provide all the necessary nutrients. Human-reared kittens tend to be very affectionate with humans as adults and sometimes more dependent on them than kittens reared by their mothers, but they can also show volatile mood swings and aggression. Depending on the age at which they were orphaned and how long they were without their mothers, these kittens may be severely underweight and can have health problems later in life, such as heart conditions. The compromised immune system of orphaned kittens (from lack of antibodies found naturally in the mother's milk) can make them especially susceptible to infections, making antibiotics a necessity.
The cat (Felis catus) is a small carnivorous mammal. It is the only domesticated species in the family Felidae and often referred to as the domestic cat to distinguish it from wild members of the family. The cat is either a house cat or a farm cat, which are pets, or a feral cat, which ranges freely and avoids human contact. A house cat is valued by humans for companionship and for its ability to hunt rodents. About 60 cat breeds are recognized by various cat registries.