Feeding cats a balanced diet is a difficult task, if only for the fact that they depend on nutrients that they can only naturally find in animal sources. This includes taurine, which is important in many ways, including heart muscle function, normal vision, normal pregnancy and a healthy immune system. Taurine is an essential nutrient that is obtained from the diet, either in a natural form through consumption of meat and offal or as a supplement.
It is similar with that Vitamin A. It is important for vision, bone and tooth growth, reproduction, healthy skin and mucous membranes. Like taurine, it is ingested through food. The cat can do this by consuming animal products, especially liver and fish oils, or by taking a dietary supplement.
As a last example Vitamin D -more precisely D3- (important for bone metabolism). Cats cannot produce this vitamin themselves either. Therefore, it must be supplied to them with their food. The vitamin is particularly found in liver, egg yolk or certain types of fish such as salmon.
As you can see, a meatless diet is very difficult to implement and vegan cat feeding is impossible. Also remember that cats are picky eaters. Your cat may simply refuse a change in diet. Do not force them by starving them, because a radical diet can lead to life-threatening lipidosis in our feline darlings.