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THE DIGESTIVE SYSTEM OF VERTEBRATES

MAMMALS: Kangaroo  (rat kangaroo listed separately)

Red kangaroo (photo by Dr. Ed Stevens)    < go to CD



Eastern grey kangaroo (Macropus giganteus) digestive tract (Stevens & Hume 1995)



Figure 4.8. Kangaroo stomach showing the region of stratified squamous epithelium.  (Modified from Stevens and Hume 1995)  (CD Figure 5.8)



Figure 4.9.  Kangaroo expanded forestomach.  E designates esophageal entrance, and P designates pylorus.  (Modified from Stevens and Hume 1995.)  (CD Figure 5.9)


Table 6.6.  Mean retention time for herbivorous forestomach fermenters (CD Table 7.6)

Although digesta retention times are affected by differences in the diet, and in the body temperatures of the bird, sloth and other eutherian mammals, foregut fermenters retain particulate digesta as long or longer than fluid digesta. Most small forestomach fermenters retain fluid and particles for equal lengths of time, but particles are selectively retained by the forestomach of large species and this tends  to increase with an increase in dietary fiber. (modified from Stevens and Hume 1995)



Figure 6.7.  Relationship between cell wall digestibility and mean retention time (MRT) of fiber by foregut and colon fermenters on a grass hay diet. Red circles represent foregut fermenting ruminants and camels; a) barasigha, b) eland, c) nilgae, d) wapiti, e) water buck, f) gaur, g) giraffe, h) gemsbok, i) African buffalo, j) American bison, k) dromedary camel, and l) bactrian camel. Blue circles represent colon fermenting a) Grevy’s zebra, b) mountain zebra, c) plains zebra, d) Asian tapir, e) American tapir, f) Asian wild ass, g) African elephant, h) Asian elephant, i) black rhino, j) Indian rhino, and k) white rhino. R2 = 0.66 for the ruminants and camels and 0.26 for colon fermenters. Yellow triangles represent; (1)  red kangaroos on an alfalfa diet, river hippos on an (2) alfalfa hay or (3) grass diet, and (4) sloths on a diet of Ceropia palmata foliage. Data for ruminants, camels, hippos, and colon fermenters are from Foose (1982). Data on red kangaroos are from Hume (1999) and data on the three-toed sloth are from Foley et al. (1995) and Foley (personal communication.)  (CD Figure 7.7)



Figure 6.6.  Variations in digestive strategy with respect to dietary combinations of refractory carbohydrates (cellulose, hemicellulose, and lignin), and protein (A) or fermentable solutes (B). The size and shape of the boxes represent the range of diets within which each digestive strategy is postulated to be effective. (From Cork et al. 1999.)  (CD Figure 7.8)


Table 7-4  (CD Table 8.5)

All data on adult specimens are expressed in µmoles substrate/minute per gram (wet weight) of mucosa.  (modified from Vonk and Western 1984)


Table 8.2  (CD Table 9.2)



Table 8.5.  Short-chain fatty acids in the foregut of herbivorous birds and mammals. (CD Table 9.5)

Dashes indicate absence of information. Contributions of SCFA to maintenance energy were estimated from the rate of SCFA production by in vitro isotope dilution or measurements of digesta flow. Total maintenance energy was either calculated as twice  the BMR or assumed to be equivalent to ad libitum digestible energy intake in captive, nonreproducing, adult animals. (From Stevens and Hume 1995)