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.
The ideal milk is to use replacement queen's milk. If you do not have any, then use boiled water to feed the kitten and purchase some replacement milk immediately. If the kitten seems very hungry, then you can add one teaspoon of glucose powder to one cup of boiled water. However, you should only do for one feeding.