Gastrointestinal is an adjective meaning of or pertaining to the stomach and intestines. A tract is a collection of related anatomic structures or a series of connected body organs.
You can obtain mother's milk replacer for young kittens at many of the pet stores in the area. When the kittens are 8 weeks or older, they no longer need the milk but may enjoy it anyway. Milk that has been specially processed for cats to consume safely is available from many local groceries. Water. Keep clean, fresh water available to your kitten at all times.
Some owners find it easier to feed newborn kittens from a one or three milliliter syringe and switch to a bottle when the kitten is two weeks old. (of course, the needle needs to be removed first) During the first week, feed the kitten every two hours. During the next three weeks, feed them every three hours. When the kittens are four weeks old, they can be fed every six to twelve hours depending on how much solid food they are already eating.