Essential fatty acids (like omega 3 and omega 6 fatty acids) and fat soluble vitamins (Vitamin A, Vitamin E, Vitamin, D, Vitamin K). The plain fat is a nutrient too.
Kittens, generally, can begin to use a litter box at about four weeks of age, and a kitten being raised without its mother or adult cat will take slightly longer to litter train; so, keep this in mind when you begin the task of litter training your kitten. - Place the kitten in the box 1/2 hour after play or meals.
Kittens this age will begin to eat regular cat food, and will begin to use a litter box. They are still quite small at this age. they will weigh anywhere from 1/2 lb to 1 lb. 6-7 weeks- Kittens are quite active and weigh about 1 pound to 1 an 1/2 pounds Their eye color, changes from blue to its permanent color. May still be friendly and approach people.