This is a *very* long scholarly article overviewing microbial involvement in vertebrate animal digestion (hey, it includes data on whales and gorillas!):
http://physrev.physiology.org/cgi/content/full/78/2/393#SEC2_6 ...An enlarged colon is the principal site for microbial fermentation in many of the larger herbivorous mammals, such as the perissodactyls, elephants, wombats, sirenians (manatees and dugongs), orangutans, and gorillas (Fig. 7). Perissodactyls include the equids and white rhinos, which graze on grasses and forbs, and the tapirs and black rhinos, which are browsers (271). Some equids, such as the African and Asiatic asses, inhabit semiarid and arid environments. Elephants are found in the forests and steppes of Asia and Africa, where they graze on grasses and browse on shrubs and small trees and the bark of large trees (4)... ...A large compartmentalized or haustrated stomach is the principal site for microbial fermentation in the remainder of the large herbivores (Fig. 8). This includes most artiodactyls, and the sloths, macropod marsupials (kangaroos, wallabies and rat-kangaroos), and colobus and langur monkeys. The artiodactyls can be divided into the suborders Ruminantia (bovids, sheep, goats, giraffe, antelope, and deer), Tylopoda (new and old world camels), and Suiformes (hippos, peccaries, Malayan pig deer, and pigs). All but a few species of pigs are herbivores with an enlarged, compartmentalized stomach. The stomach of Ruminantia is divided into a large multicompartmental forestomach (reticulum, rumen, and omasum) and a secretory compartment (abomasum) that is similar to the entire stomach of most other vertebrates... (much further down) ...Much of our understanding of gut microbiology derives from early studies of the ruminant forestomach. During the first weeks after birth, the forestomach becomes colonized with Escherichia coli aerogenes and streptococci, which are joined by lactobacilli in the suckling animal (79). Weaning is followed by development of the extremely complex microbiota that are characteristic of adult animals (3, 142, 277). Culture counts give estimates of 1010 to 1011 of predominantly anaerobic bacteria per gram of fluid in rumen contents. Microscopic counts, which include organisms that are dead or require specific culture media, give higher numbers. Table 5 lists the principal bacterial species found in the rumen of sheep and cattle and their fermentative properties. Their interactions are discussed by Van Soest (269), but they collectively ferment carbohydrate into SCFA, utilize protein and other nitrogenous compounds for synthesis of microbial protein, synthesize B vitamins, hydrolyze lipids, and hydrogenate fatty acids... The table below this lists a number of rumen-living microbes and their products of fermentation; only 2 were methane-producers, but quantities were not given. ...The numbers of bacteria in the mammalian midgut are generally much lower than those in the rumen. Savage (235) reported that the human small intestine contained 104 to 106 viable, predominantly anaerobic organisms per gram of digesta. Rambaud (217) also reported counts of 105 bacteria/ml in the small intestinal contents of two-thirds of the human subjects. These were predominantly aerobes, but the number increased to 108/ml, with the appearance of enterobacteria and strict anaerobes in the ileum of one-third of the subjects. Mackie and Wilkins (175) found that the counts of anaerobic bacteria in grass-fed horses ranged from 106/g in the duodenum to 108/g in the ileum... Ah, diagram of carbohydrate fermentation in ruminants: (getting closer to the data I seek) http://physrev.physiology.org/cgi/content/full/78/2/393/F11 BINGO! "Rumen gases vary in both their rate of production and their composition with time after feeding (276). Carbon dioxide is derived from fermentation of carbohydrate and the neutralization of SCFA with HCO3 . Methane production is directly proportional to acetate production and inversely proportional to the production of propionate, but it also depends on other factors that affect the growth and replication of methanogenic organisms. It appears to be almost totally derived from reduction of formate, H2 , and CO2 , which accounts for the low concentrations of H2 in the rumen, except for the first few days of a fasting period. Nitrogen and O2 are added from swallowed air, and N2 can diffuse into the rumen from the blood as well. Oxygen is rapidly reduced by rumen microorganisms, and some of the CO2 is directly absorbed into the blood, but much of the CO2 and most of the CH4 produced in the rumen is removed by eructation. Kleiber (159) found that an adult cow on a diet of 5 kg hay lost 191 liters of CH4 through eructation and flatulence, which was equivalent to a 10% loss of their daily digestible energy intake." About 190 liters of methane/day/cow... Wow. Humans: "Calloway (40) reviewed information on the composition of gasses in the large intestine of dogs, rats, pigs, cattle, horses, and humans. They consisted of the same gasses as those found in the rumen (CO2 , CH4 , H2 , and N2), but with considerable variation among species and with changes in diet. It was estimated that the large intestine accounts for ~13% of the CH4 produced in the gastrointestinal tract of sheep (186). The human large intestine contained higher percentages of H2 and N2 and lower percentages of CO2 and CH4 than the rumen, and CH4 was absent in about two-thirds of the human population (169)." So only one-third of humans release methane. And hey! dinosaurs get a mention: "The extreme success of mammalian herbivores can be attributed to endothermy, an efficient masticatory apparatus and an expansion in gut capacity. The parallel success of herbivorous dinosaurs suggests that they were endotherms with an efficient masticatory apparatus and similar suite of digestive strategies, according to their body size, habitat, and the quality and availability of forage and water." Debbi Gotta Run Now Maru ;) ____________________________________________________________________________________Got a little couch potato? Check out fun summer activities for kids. http://search.yahoo.com/search?fr=oni_on_mail&p=summer+activities+for+kids&cs=bz _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
