3. Ph.D. Of

5. Proportion of Whole Stomach Weight of Calves, % Age (Days) AbomasumOmasumRumen &Reticulum 5610341 45154014 34115528 23116647 121870100 112564Adult Swenson, M. J. 1977. Dukes Physiology of Domestic Animals.

18. پایان

20. Ruminants....

22. 100-150 L 5-8 L 3-5 L Collectively, these organs occupy almost 3/4ths of the abdominal cavity, filling virtually all of the left side and extending significantly into the right.

23. The rumen papillae are key to VFA absorption; health is critical The honeycomb of the reticulum is well suited for sorting particles by size and for rumination The folds and plies of the omasum allow ingesta to be trapped and squeezed to allow dehydration prior to delivery to the abomasum RumenOmasum Reticulum

24. Ruminants: Some Basics Ruminants: Some Basics A. Rumination: re-gurgitation, re-mastication, re-insalivation, re-swallowing B. Eructation: 12-30 L per minute; 3-17 times per minute C.Digestion D. Fermentation I. Physical: I. Physical: 4 specialized stomach compartments

25. Ruminants: Some Basics Ruminants: Some Basics A. Cellulase complex B. Hemicellulases C. Lysozyme D. Nitrogen Capture (NPN) II. Chemical: II. Chemical: specialized Enzymes & Processes Because of these enzymes and abilities, ruminants can utilize feedstuffs that provide little to no nutritional benefit to non-ruminants.

26. Ruminants: Some Basics Ruminants: Some Basics A.Fiber Digestion B.Starch Digestion C. Urea Utilization

27. The nutrients presented to the cow or steer by the rumen are very different than those entering the rumen as feed.

28. Rumen Function and Development Rumen Function and Development A. The 4 compartments or four chambers: Rumen 1.Rumen: digestion and fermentation vat (VFA production) Reticulum 2.Reticulum: mixing aid (feed, water, saliva) Omasum 3.Omasum: Dehydration by compression/squeezing removes 60-70% of water from ingesta Abomasum 4.Abomasum: “true stomach”; acid secretion, lysozyme I. Organization, function, and special relationships among compartments

29. Rumen Function and Development Rumen Function and Development 1. Rumen: digestion and fermentation vat A. conditions must be maintained to support microbial growth 1. temperature, moisture, pH buffered 2. constant supply of nutrients 3. continuous removal of products of digestion/fermentation (gases, VFA, ammonia)

31. Rumen Function and Development Rumen Function and Development B. products of fermentation provide bulk of energy to animal 1. Starch and cellulose digestion 2.Anaerobic metabolism (fermentation) 3.Volatile fatty acid (VFA) production

32. Rumen ciliate protozoa Rumen ciliate protozoa

33. Rumen Function and Development Rumen Function and Development C. complex polysacharides are digested to yield sugars that are fermented to produce VFA 1. Structural polysaccharides: cellulose, hemicellulose digested by cellulases and hemicellulases 2. Cellulase is not a single enzyme, but a complex (affinity factor + hydrolytic factor) 3. Protozoa engulf starch particles to digest them 4. Microbes attach to (colonize) fiber components and secrete enzymes

35. D. Its The VFA That Provide The Bulk Of The Energy To The Ruminant 1.Bacterial sugar metabolism differs from that of aerobic organisms. 2.VFA are produced from pyruvate by fermentation Polysaccharides Galactose Sucrose Fructose Maltose Glucose Acetate, Butyrate, Propionate Some Basics

36. Digestion Fermentation All CHO Must Pass Through Pyruvate to Become VFA

37. Some Basics Non-structural polysaccharides Structural polysaccharides VFA, H + PyruvateLactate

38. E. Rumen pH Must Be Defended 1.VFAs (acids) produced must be removed 2.Passively absorbed across rumen wall 3.Helps maintain pH at 5  6.7 Some Basics 4.Saliva also provides buffering capacity 180 L per day cattle: 180 L per day (70% water entering rumen) 5.Saliva is rich in Na, K, PO 4, HCO 3

39. Rumen papillae epithelium performs at least 3 major functions: Protection Metabolism Metabolism Absorption Absorption VFA are absorbed passively; thus, the concentration gradient from lumen to blood supply must be maintained. Metabolism of some VFA within the cells of the papillae help ensure a gradient.

40. II. Rumen Development II. Rumen Development A. Newborns are not functional ruminants 1.Lack sucrase 2.Limited amylase 3.Lactase: galactose, glucose 4.Ability to digest non-starch polysaccharides precedes that for starch Some Basics

41. Rumen Development Begins Early 1.Depends on: A.Fibrous Diet B.Inoculation C.VFA Stimulation Some Basics

42. Questions