I recently came across a Twitter post of someone who rescued a kitten and was asking for care advice. The number of people who responded with advice to give the kitten cow's milk was astounding. This is one of those myths that just won't die. Thanks a lot, vintage advertisements!
Though a cat usually won't pass up a tempting bowl of milk, many cats are lactose intolerant. What comes in must come out, and that may be in the form of vomiting or diarrhea.
In similar fashion, cow's milk should not be given to kittens, as it can make them sick. The only appropriate milk in absence of the mother cat is kitten milk replacement formula. This formula can be bought at pet stores and even stores such as Target.