Coprophagy refers to animals reingesting their own feces to absorb more of the vitamins and nutrients contained in them. For the animals that practice this, one pass through their digestive system is not sufficient to extract all of the nutrients from their food.

Most people know that cattle, deer and moose chew cud. This is a form of "internal coprophagy".

Following are some references to coprophagy from selected books.
(Thanks to Julie L. for this research)

Leporids [rabbits and hares] have a unique digestive process called reingestion or refection. Two types of material are eliminated from the alimentary tract. The first consists of normal brown faecal pellets, and the second of soft greet pellets, composed of only slightly predigested plant food, which are passed mainly during the daytime rest period. These are sorted out by the animal and reingested. The whole system recalls that found in ruminants, in which a cud of vegetation is returned to the mouth from the stomach and rechewed. Reingestion has been observed in a number of species and is probably characteristic of the whole group.
- The Mammals of Canada, A.W. Banfield; pp 75-76

Like several other common animals that feed on vegetation - beaver, vole and snowshoe hare - cottontails reingest one type of their droppings. These are usually soft pellets that are voided during the day while the animal is at rest. The cottontail swallows then direct from its anus without chewing. Reingestion, or coprophagy, apparently allows for further digestion of plant material, much like cud chewing in ruminants.
- Animal Tracking and Behaviour, Donald & Lillian Stokes; p 165

To aid the digestion of food, voles practice coprophagy, reingesting their own feces to absorb more of their vitamins and nutrients. These feces are usually softer and lighter in color than the final scats, which are excreted and left alone. Rabbits, hares, and beavers also practice coprophagy. Coprophagy usually occurs during periods of rest that directly follow active periods.
- Animal Tracking and Behaviour, Donald & Lillian Stokes; pp 242 - 243

Tracks & Sign: Mammals, Birds, Other Animals Skulls