Coprophagy is the eating of excrement and is a normal nutritional behavior for rats. It is essential for the maintenance of healthy gut flora and for the recovery of nutrients.
Rats have a simple stomach as opposed to ruminants (which have compartmentalized stomachs) such as cows, goats, and sheep. Without the multiple digestive compartments to aid in breaking down food, essential nutrients are not digested and are passed in the feces.
In a simple stomach digestive system the ingested food moves more rapidly than in the ruminant system. Microbial fermentation of the food occurs in the caecum, which is a pouch located at the beginning of the colon (also known as hind-gut fermentation). Cellulose (plant) fibers are not effectively broken down during this process.
Eating of the feces allows the recovery of nutrients that were not utilized during the first pass through the digestive system.
Rats produce two types of fecal pellets. One is a dark firm pellet and the other is soft. The soft feces is held within the anus and usually eaten directly from the anal orifice. It is covered with a mucus membrane that, once entering the stomach, slows down the digestive process of the feces and promotes fermentation. This allows a more effective breakdown of nutrients.
Rats will regulate the amount of feces eaten according to their nutritional needs. Rats will eat between 0-11 percent of their own feces when fed a nutritionally complete diet. Thiamin and pantothenic acid deficiencies will cause a marked increase in coprophagy. Preventing rats from eating their feces can lead to deficiencies of vitamin K, complex B vitamins, and biotin and can cause other vitamin deficiencies to develop. Rats, when not permitted to ingest their fresh feces show a stunted growth rate. Even if allowed to eat only the dry feces the benefits of coprophagy are still not attained.
- Besselsen, D. (n.d.). Biology of Laboratory Rodents. Retrieved December 18, 2008, from http://www.uac.arizona.edu/VSC443/rodentbio/rodentbio.html.
- Fajardo, G., & Hörnicke, H. (1989). Problems in estimating the extent of coprophagy in the rat. Br J Nutr, 62(3), 551-61. Retrieved December 18, 2008, from the Medline database.