swine 10^8: human 10^7: cattle 10^6: rabbit 10^4 bacteria/g dry weight
||Sorlini, C., Brusa, T., Ranalli, G. et al. Quantitative determination of methanogenic bacteria in the feces of different mammals, Current Microbiology, January 1988, Volume 17, Issue 1, pp 33–36 doi: 10.1007/BF01568816
||P.33 right column bottom paragraph: "Determination of the number of methanogenic bacteria and anaerobic
heterotrophic bacteria: The bacteria count was done in quintuple by a multiple tube, most probable number (MPN) technique [ref 3]. At the end of the incubation period the cultures of
methanogenic bacteria were observed with a fluorescence microscope, and the head space gas of each tube was separately analyzed by gas chromatography. The presence of methanogenic bacteria was shown by the presence of methane in the analyzed
gas and of fluorescent cells in the culture."
||Abstract: "In this research on fresh human, cattle, swine, and rabbit feces, methanogenic bacteria were found in all samples examined, at the following concentrations per gram dry weight: swine, 10^8 human, 10^7 cattle, 10^6 and rabbit, 10^4."