Feeding and diet:- Cats

Cats are classified as obligate carnivores, because their physiology is geared toward efficient processing of meat, and lacks efficient processes for digesting plant matter. The cat cannot produce its own taurine (an essential organic acid) in its own body and as it is contained in flesh, the cat must eat flesh to survive (see Taurine and cats). Similarly as with its teeth, a cat's digestive tract has become specialized over time to suit meat eating, having shortened in length only to those segments of intestine best able to break down proteins and fats from animal flesh. The trait severely limits the cat's ability properly to digest, metabolize, and absorb plant-derived nutrients, as well as certain fatty acids. For example, taurine is scarce in plants but abundant in meats. It is a key amino sulfonic acid for eye health in cats. Taurine deficiency can cause a condition called macular degeneration wherein the cat's retina slowly degenerates, eventually causing irreversible blindness.
Despite the cat's meat-oriented physiology, it is still quite common for a cat to supplement its carnivorous diet with small amounts of grass, leaves, shrubs, houseplants, or other plant matter. One theory suggests this behavior helps cats regurgitate if their digestion is upset; another is that it introduces fiber or trace minerals into the diet. In this context, caution is recommended for cat owners because some houseplants are harmful to cats. For example, the leaves of the Easter Lily can cause permanent and life-threatening kidney damage to cats, and Philodendron are also poisonous to cats. The Cat Fanciers' Association has a full list of plants harmful to cats.
There are several vegetarian or vegan commercially-available cat foods supplemented with chemically-synthesized taurine and other added nutrients that attempt to address nutritional shortfalls.
Cats can be selective eaters (which may be due in some way to the aforementioned mutation which caused their species to lose sugar-tasting ability). Unlike most mammals, cats can voluntarily starve themselves indefinitely despite being presented with palatable food, even a food which they had previously readily consumed.
Some cats have a fondness for catnip, which is sensed by their olfactory systems. While they generally do not consume it, they will often roll in it, paw at it, and occasionally chew on it.