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THE DIGESTIVE SYSTEM OF VERTEBRATES

MAMMALS: Bovid, domestic

Jersey cow (photo by Biomedical Communication Department, College of Veterinary Medicine, N. C. State University, Raleigh, NC 27606)



Figure 4.9.  Ox expanded forestomach.  E designates esophageal entrance, P designates pylorus, 1 designates omasum, and 2 designates abomasum.  (Modified from Stevens and Hume 1995.)  (CD Figure 5.9)



Figure 4.10.  The large intestine of the ox.  (Modified from de Lahunta and Habel 1986.)  (CD Figure 5.10)



Figure 5.3.  Diagrammatic sections of bovine reticulorumen and omasum.  Structures and compartments of major importance are numbered as follows:  1) cardia, 2) reticulo-omasal orifice, 3) reticulum, 4) cranial sac of rumen, 5) dorsal sac of rumen, 6) caudodorsal blind sac, 7) ventral sac of rumen, 8) caudoventral blind sac, 9) ruminoreticular fold, 10) cranial pillar, 11) right longitudinal pillar, 12) caudal pillar, 13) dorsal coronary pillar, 14) ventral coronary pillar, 15 ) omasum, 16) omasal canal, 17) omasal pillar, 18) omaso-abomasal orifice, 19) omasal lamina (leaf), 20) abomasum.  (From Sellers and Stevens 1966.)  (CD Figure 6.3)



Figure 5.6.  Movement of digesta through the bovine omasum.  Closed arrows show movement of digesta and open arrows show movement of forestomach walls. Diagrammatic axial section (see Fig. 5.3) shows the cranial reticulum (1), reticulo-omasal orifice (2), omasal leaf portion of omasal body (3), omasal canal (4) and cranial abomasum (5).  A: All structures are relaxed during much of the cyclic contraction of the forestomach.  B: During the second reticular contraction, the reticulo-omasal orifice and omasal canal are pulled ventrally, producing a negative pressure in the canal and a closing and then opening of the orifice, which results in aspiration of digesta from the base of the reticulum.  C: Primary contraction of the rumen is associated with a primary contraction of the reticulo-omasal orifice and omasal canal, forcing fluid and small digesta particles between the leaves of the omasal body and into the abomasum.  These events are followed by relaxation of these structures (D), and repeated if the forestomach undergoes a secondary contraction.  E: At intervals that vary and are unrelated to the cyclic contractions of the forestomach, a wave of contraction passes over the omasal body, releasing its contents into the abomasum. (From Stevens and Hume 1995.)  (CD Figure 6.6)



Figure 5.7.  Reticuloruminal cycles during rumination in cattle. Numbers 1 and 2 mark first and second reticular contractions seen with every cycle and the x marks the extra reticular cycle at the regurgitation stage (R) of rumination. The remasticated bolus is swallowed (D) just prior to the next reticulorumen cycle. The AP on the reticular tracing is a registration of abdominal press at the time of eructation (E).  (From Stevens and Sellers 1968.)  (CD Figure 6.7)


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)


Table 7.5b.  (CD Table 8.6b)

Enzymatic activity is designated as + (present), trace or 0 (absent). Results in brackets indicate use of and alternate substrate. All data from adult specimens. (from Vonk and Western 1984 plus perissodactyla data from Roberts 1975)


Table 7.7.  (CD Table 8.10)

Enzyme activities expressed as the equivalent amount of bovine trypsin (casein or BAEE) or chymotrypsin (BTEE) under the same conditions. *A: 200-1,200 g RNase per gram pancreatic tissue; B: 20-100 g per gram pancreatic tissue; C: 0-20 µg RNase per gram pancreatic tissue. (from Vonk and Western 1984)


Table 7.8.  (CD Table 8.11)

0, no absorption or transfer; + to +++, degrees of absorption or transfer. (from Brambell 1970)


Table 8.2.  (CD Table 9.2)




Figure 8.5. Composition of rumen gases in a dairy cow on a ration of hay and grain (Washburn and Brody 1937) (CD Figure 9.5)


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)