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.
Mom needs lots of good quality wet food so that the babies get the best nourishment possible from her while they are in their growth phase. Kittens will nurse every 1-3 hours for the first three weeks. Only when they hit four or five weeks old will they be ready to start weaning off mom and onto wet food.