Coprophagia  or coprophagy is the consumption of feces. The word is derived from the Greek copros, "feces" and phagein, "to eat". Coprophagy refers to many kinds of feces-eating, including eating feces of other species (heterospecifics), of other individuals (allocoprophagy), or one's own (autocoprophagy) - those once deposited or taken directly from the anus.
In humans, coprophagia has been described in individuals with mental illnesses, as well as an unconventional sexual act since the late nineteenth century. Some animal species eat feces as a normal behavior, in particular in the Lagomorpha (rabbits, hares, and pikas) doing so to allow tough plant materials to be digested more efficiently by passing twice through the digestive tract. Other species may do so only under unusual conditions.
Coprophagous insects consume and redigest the feces of large animals. These feces contain substantial amounts of semi-digested food, particularly in the case of herbivores, owing to the inefficiency of the large animals' digestive systems. Two feces-eating insects are certain species of fly and the dung beetle. In regards to the dung beetle, their diet is mainly in the form of the microorganism-rich liquid component that is present in the dung of mammals, while they take advantage of the fibrous material in the dung for the female to lay her fertilized eggs in.
Termites eat one another's feces as a means of obtaining their hindgut protists. Termites and protists have a symbiotic relationship (e.g. with the protozoan that allows the termites to digest the cellulose in their diet). For example, in one group of termites, there is a three-way symbiotic relationship: termites of the family Rhinotermitidae, cellulolytic protists of the genus Pseudotrichonympha in the guts of these termites, and intracellular bacterial symbionts of the protists.
Domesticated and wild mammals are sometimes coprophagic, and in some species this forms an essential part of their method of digesting tough plant material.
Species within the Lagomorpha (rabbits, hares, and pikas) produce two types of fecal pellets: hard ones, and soft ones called cecotropes. Animals in these species reingest their cecotropes, to extract further nutrients. Cecotropes derive from chewed plant material that collects in the cecum, a chamber between the large and small intestine, containing large quantities of symbiotic bacteria that help with the digestion of cellulose and also produce certain B vitamins. After excretion of the soft cecotrope, it is again eaten whole by the animal and redigested in a special part of the stomach. The pellets remain intact for up to six hours in the stomach; the bacteria within continue to digest the plant carbohydrates. This double-digestion process enables these animals to use nutrients that they may have missed during the first passage through the gut, as well as the nutrients formed by the microbial activity and thus ensures that maximum nutrients are derived from the food they eat. This process serves the same purpose within these animals as rumination (cud-chewing) does in cattle and sheep.
Cattle in the United States are often fed chicken litter. There are concerns that the practice of feeding chicken litter to cattle could lead to bovine spongiform encephalopathy (mad-cow disease) because of the crushed bone meal in chicken feed. The U.S. Food and Drug Administration regulates this practice by attempting to prevent the introduction of any part of a cow's brain or spinal cord into livestock feed. Other countries, like Canada, have banned chicken litter for use as a livestock feed.
The young of elephants, giant pandas, koalas and hippos eat the feces of their mothers or other animals in the herd, in order to obtain the bacteria required to properly digest vegetation found in their ecosystems. When such animals are born, their intestines are sterile and do not contain these bacteria. Without doing this they would be unable to obtain any nutritional value from plants.
Hamsters, guinea pigs, chinchillas, hedgehogs and naked mole-rat eat their own droppings, which are thought to be a source of vitamins B and K, produced by gut bacteria.Gorillas have been recorded to consume their feces extremely rarely, possibly out of boredom, a desire for warm food, or to reingest seeds contained in the feces.
Lewin reported that "... consumption of fresh, warm camel feces has been recommended by Bedouins as a remedy for bacterial dysentery; its efficacy (probably attributable to the antibiotic subtilisin from Bacillus subtilis) was anecdotally confirmed by German soldiers in Africa during World War II".
Centuries ago, physicians tasted their patients' feces, to better judge their state and condition.
The 120 Days of Sodom, a novel by the Marquis de Sade written in 1785, is full of detailed descriptions of erotic sadomasochistic coprophagia.Thomas Pynchon's award-winning 1973 novel Gravity's Rainbow contains a detailed scene of coprophagia.François Rabelais, in his classic Gargantua and Pantagruel, often employs the expression mâche-merde or mâchemerde, meaning shit-chewer. This in turn comes from the Greek comedians Aristophanes and particularly Menander, who often use the term skatophagos (). The Austrian actor and pornographic director Simon Thaur created the series "Avantgarde Extreme" and "Portrait Extrem", which explores coprophagy, coprophilia and urolagnia. Modern Russian writer Vladimir Sorokin's novel Norma describes a society where coprophagia is institutionalised and mandatory.
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