Vitamin A, so called retinol, is the major element for animal vision, immune function, and skin health. Retinol will be converted to retinal, which forms the necessary rhodopsin to support normal night vision in the visual process. Additionally, vitamin A is vital for animal growth, bone development, and reproductive capacity; it enhances the immune system, improving overall disease resistance in animals. Its impact on cellular function is profound, involving the regulation of carbohydrate, fat, and protein metabolism. Animal-based foods such as fish liver oil, whole milk, and fish meal are its primary sources. Plant-based materials contain precursors like beta-carotene, found in green plants such as grass, clover, alfalfa, and carrots. Ruminants, for instance, can effectively convert beta-carotene into vitamin A as cats need to obtain vitamin A directly from their diet.