Cat food is food specifically designed for consumption by cats. As obligate carnivores, cats have specific requirements for their dietary nutrients, namely nutrients found only in meat, such as taurine, arginine, and Vitamin B6. Certain nutrients, including many vitamins and amino acids, are degraded by the temperatures, pressures and chemical treatments used during manufacture, and hence must be added after manufacture to avoid nutritional deficiency. History During the 19th century and early 20th centuries, meat for cats and dogs in London, frequently horse meat, was sold from barrows (hand–carts) by traders known as Cat's Meat Men or Women. Henry Mayhew estimated in London Labour and the London Poor (1851) that the total number of cats in London might be 300,000. Each cat's meat seller had a particular route and served a few hundred households, their approach marked by mewing cats. The idea of preparing specialized food for cats came later than dog food and dog biscuits. This was likely due to the idea that cats could readily fend for themselves. In 1837, a French writer Mauny de Mornay critiqued this idea: In 1844, another French writer, Nicolas Jean-Baptiste Boyard, expanded on this idea: He goes on to say that it is all the more unreasonable to expect a cat to live from hunting in that cats take mice more for amusement than to eat: "A good cat takes many and eats few." By 1876, Gordon Stables emphasized the need to give cats particular food: In the same year, an advertisement for Spratt (better known for making dog food) said that their cat food entirely superseded "the unwholesome practice of feeding on boiled horse flesh". And, in another book on cats, Stables recommended the company's food: Spratt, which began by making dog biscuits, appears to also have been the first commercial producer of cat food. Natural diet Cats are obligate carnivores—meaning, they are true carnivores and depend upon the nutrients present in animal flesh for their dietary needs. Even domesticated cats will relish freshly killed meat from rodents, rabbits, amphibians, birds, reptiles and fish, whether through hunting or by having it provided by humans, but cats are also opportunistic feeders and will readily take cooked food as well as dried cat food when offered, if that food is palatable. The natural diet of cats therefore does not include any vegetable matter, although cats have been known to eat certain plants and