Animals cannot sustain a healthy life if they are fed on a diet having only carbohydrates, fats and proteins. They also require vitamins in small quantities in the range of milligrams or micrograms. These function as coenzymes in metabolic reactions. You might find it useful to re-read the list of vitamins, their main functions and their dietary sources. Table gives a more detailed list of vitamins important in animal and human nutrition along with their diverse functions.
The synthetic ability for vitamins also varies among different animal species and those essential vitamins that the animal cannot synthesise must come from its dietary sources. For instance, most animals can synthesise ascorbic acid but humans cannot. We also depend on intestinal bacteria to synthesise vitamin K and BI2. Fat soluble vitamins like A, D, E and K can be stored in the fat deposits of the body but vitamins that are water soluble like B or C need to be supplied continually as they are lost through urine.