Table 4.

Total number of prokaryotes in some representative animals

Animal	Organ	Cells/ml or cells/g	Organ contents*	No. of animals†	No. of cells, × 1023	Refs.
Human	Colon	3.2  ×  1011	220 g	5.6  ×  109	3.9	45, 46
Cattle	Rumen	2.1  ×  1010	106 liter	1.3  ×  109	29.0	47, 48
Sheep and goats	Rumen	4.4  ×  1010	12 liter	1.7  ×  109	9.0	47, 48
Pigs	Colon	5.4  ×  1010‡	9 liter	8.8  ×  108	4.3	49, 50
	Cecum	2.8  ×  1010‡	1 liter	8.8  ×  108	0.3	49, 50
Domestic birds§	Cecum	9.5  ×  1010	2 g	1.3  ×  1010	0.024	51, 52
Termites	Hindgut	2.7  ×  106¶		2.4  ×  1017	6.5	53

^*Organ contents in volume or grams of wet weight. For comparison, the volume of the human colon is 0.5 liter. For domestic birds, weight wet was calculated from a volume of 2 ml assuming that 1 ml - 1 g wet weight. 

^†Values from the FAO Production Yearbook (54), except for the termites value which was from ref. 55. 

^‡The direct count was assumed to be 2.7 × viable count (56). 

^§Includes chickens, ducks, and turkeys. 

^¶Per termite.