Kittens require a high-calorie diet that contains more protein than the diet of adult cats. Young orphaned kittens require 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 of their necessary nutrients.
Hand-reared kittens tend to be affectionate to humans as adults and more dependent on them than those reared by their mothers, but they can also show volatile mood swings and aggression. Orphaned kittens can be severely underweight and as such 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 when caring for such kittens.