DIGESTION

1. DIGESTION ANSC 101

2. Definition • Digestion is all of the chemical and physical changes that food undergoes to be absorbed. • Absorption takes place as nutrients enter the body from the digestive tract.

3. Mouth Esophagus Stomach Small intestine Large intestine Liver, gall bladder pancreas GI Tract – Digestive System

5. MOUTH • Teeth • Tongue • Salivary glands

6. Esophagus • Birds • CROP • Mammals

7. Stomach • Complexity varies • Simple in monogastrics (nonruminants) • 4-chambered complex stomach of ruminant

8. Functions of Stomach • STORAGE • Chemical Digestion

9. Non-Ruminant Stomach • 4 regions • Esophageal • Cardiac • Fundic • Pyloric

10. Poultry • “Stomach” is called PROVENTRICULUS • Has same functions as mammal

11. Gastric Secretions • HCL • Activates pepsinogen to pepsin • Does some digestion itself • Gastric Enzymes • Pepsin • Lipase • Renin • Mucin • Intrinsic Factor (for absorbing B12)

12. Ruminant Stomach • 4 compartments • Rumen – big fermentation vat • Reticulum – “hardware stomach” • Omasum – “many plies” • Abomasum – “true stomach”

14. Rumen Microbiology • Bacteria do 3 things • Digest CHO to VFA’s (including cellulose) • Remodel proteins, manufacture essential amino acids and utilize NPN • Manufacture B vitamins

15. Summary of Rumen Action • CHO ——> VFA’s • Proteins ——> Bacterial protein • Fats ——> hydrogenated but not much utilization • B Vitamins ——> synthesized • Vitamins ADE ——> needed in diet

16. Small Intestine • Duodenum • Jejunum • Ileum

17. Digestive Juices • Bile • Produced in the LIVER • Stored in the Gall Bladder • Pancreatic juice • Exocrine secretions • Sodium carbonate and bicarbonate • Enzymes • Endocrine secretions • Insulin • Glucogon

18. Digestive Juices continued • Secretions from small intestine wall • They digest disaccharides, peptides, etc to forms that can be absorbed

19. Absorption • Molecules must get from gut lumen into brush border of epithelial cells, then across cells into blood or lymph. • Occurs by diffusion, facilitated absorption and active absorption.

20. Large Intestine • Ascending, transverse and decending colon • FUNCTIONS: • Storage • Absorption of water • Special role of cecum

21. Cecum • Blind pouch at junction of small and large intestine • Developed in nonruminant herbivores (horses, rabbits) • Provides post-absorptive fermentation vat • Digests cellulose, Does NOT provide protein

22. Horse, Rabbit

23. Metabolism defined | CHO • Use by the body of nutrients and metabolites • Carbohydrates – converted to tiny amounts of glycogen, used for blood sugar, or converted to ATP (energy), stored as fat

24. Metabolism of Fats • Go to liver, then to fat storage, or used for energy

25. Metabolism of Proteins • Amino acids enter blood stream and supply cells with amino acids for protein synthesis • Amino acids not quickly used are deaminated and used for energy

26. Metabolism of Energy • Energy in the chemical form of ATP is either used by the tissues or stored in animals as fat

27. Metabolism of Vit’s & Minerals • Vitamins are involved in tissues throughout the body, maintaining structures and participating in chemical reactions • Minerals make up structural components and activate enzymes, maintain water balance, and more.

28. End of Digestion, 101 • Next we will consider where animals will GET those nutrients: • FROM FEEDS

29. Animal Feeds • 2 major catagories of energy-providing feeds are: • Concentrates • Roughages

30. Concentrates • Grains • High in energy, low in fiber, low in protein, low protein quality • Protein supplements • From oil seeds (like soybean meal) • From animal byproducts, fish byproducts, etc.

31. Roughages • Not used or used poorly by nonruminants • CATAGORIES • Grasses • Legumes • Crop residues

32. Grasses • Grow “everywhere” • Moderate energy source • Low protein source • Low calcium levels • Good for meeting maintenance needs

33. Legumes • Moderate sources of energy • High protein levels • High calcium levels • Not adapted to grow well everywhere • Where they do grow, they increase soil fertility

34. Legumes • Alfalfa • Red clover • White clover • Sweetclover • Alsike

35. Crop Residues • Provide bulk • Some but low levels of energy • Useful in helping meet maintenance • Very cheap except for processing and transportation costs

36. Crop Residue - Corn Stover

37. Forages can be fed as: • Pasture • Hay • Silage

38. Pasture

39. Hay

40. Silage

41. Ration Balancing • The task of meeting the animals nutrient requirements with the feeds provided to the animal

42. Ration Balancing • Determine animal’s requirements • From NRC, Extension publications, etc. • Get feed’s nutrient content • From analysis or feed tables • DO THE MATH • By hand or • By computer program

43. Example by Hand • Say pig needs 16% CP, & using Corn with 8% CP and Suppl. with 36% CP. 16 = .08X + .36(100-X) 16 = .08X + 36 - .36X 16 – 36 = .08X - .36X - 20 = - .28X X = -20X/-.28X = 71.4% corn 100 – X = 28.6% supplement

44. Example by Computer if there is time

45. Feeding programs • Pigs and poultry are fed primarily “simple” diets based on corn for energy, SBM for protein, and fortified with vitamins and minerals. • Full feed growing/finishing pigs • Limit feed pregnant sows & gilts • Use antibiotics judiciously

46. Beef and Sheep • Summer rely on range, pasture when possible • Winter: need preserved feeds: • Hay • Silage • Grain as needed

47. Feed cows, ewes according to stage of production • Needs are low at maintenance • Needs increase in last 1 /3 gestation • Needs are high during lactation • Maintain animal’s body condition

48. Feeding Beef Cows • For MOST, that means: • Spring & summer = Pasture • Fall – Winter = Preserved feeds • Late Winter (late gestation) supplement • Grain • Protein as needed • Test hay to know what you are feeding

49. Allow calves to grow (backgrounding) • Then place in feedlot on high energy feeds (grain)

50. Feeding Dairy Cattle • Requirements are very high due to high milk production • Intake is high (4% BW vs ~2% for beef) • Feed grain for high production (up to 60% of total DM)