BASIC FOODS Carbohydrates proteins and fats Cannot be absorbed in native form Require to be digested to absorbable form CARBOHYDRATES IN FEED Mostly Polysaccharides Some disaccharides also Di and poly ID: 1034927
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1. DIGESTION OF VARIOUS FOODS
2. BASIC FOODSCarbohydrates, proteins and fatsCannot be absorbed in native formRequire to be digested to absorbable form
3. CARBOHYDRATES IN FEEDMostly PolysaccharidesSome disaccharides alsoDi and poly saccharides are formed By binding of two or more mono saccharidesOne hydroxyl group from a monosaccharide andHydrogen ion from the next one are removed Thus a water molecule is removedAt the sites of removal a glycosidic bond is formedDuring digestionRemoved water is returnedThus separating the monosaccharidesThis process is called hydrolysis
4. HOHHOHHHOOHHGlycosidic Bond
5. PROTEINS IN FEEDFormed by amino AcidsBound togeher by petide bondsIn each peptide linkageA hydroxyl group and a hydrogen ion are removed from two successive amino acidsDigestion occurs by hydrolysisThe water molecule removed is returned
6. CCRHNOHOHHCCRHNOHOHHPeptide Bond
7. FATS IN FEEDAlmost entirely made up of triglyceridesThree fatty acid molecules condensed with a glycerol moleculesThree molecules of water are removedDuring digestionLipases return the three molecules of water to each triglyceride moleculeSplits away glycerol from fatty acidsThus this process is also hydrolysis
8. HHCHCHHHCHCHHHCHCHHHCHCHHCOHOHHCHCHHHCHCHHHCHCHHHCHCHHCOHOHHCHCHHHCHCHHHCHCHHHCHCHHCOHOHCHHCHCHOHHHOOGLYCEROLFATTY ACIDFATTY ACIDFATTY ACIDTRIGLYCERDIDE
9. BASIC PROCESS OF DIGESTIONOf all the nutrients is hydrolysisOnly difference is the specificity of enzymes
10. DIGESTION OF CARBOHYDRATES starchesMaltose & 3-9 glucose polymersGlucoseSalivary amylase (Pig & man) 20-40%Pancreatic amylase -50-80%sucrase, maltase, isomaltase & lactase in the enterocytes on villiSalivary amylase continues to act in stomach till the gastric pH falls ≤ 4.0Pancreatic amylase more powerful than salivary amylaseWithin 30min after chyme reaches duodenum all the carbohydrates are digested
11. DIGESTION OF PROTEINS ProteinsProteosesPeptonesPolypeptidesDi-, Tri- or polypeptides & Amino acidsPepsin in gastric juiceEffective pH 2.0 -3.0Pancreatic Trypsin, Chymotrypsin, Carboxy peptidase, elastaseAmino acidsPeptidases in enterocytes on villi
12. DIGESTION OF FATS TriglyceridesEmulsified fatFatty acids & 2 monoglyceridesMicellesAgitation in stomachBile salts and lecithin in duodenumLingual & Gastric lipase - < 10%Pancreatic lipaseBile salts
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14. ABSORPTION
15. GENERAL FEATURES OF ABSORPTIONTransfer of digested food from GIT to circulationCirculation conveys absorbed materials to tissues for processing, storage or utilizationNo absorption occurs in mouthSmall intestine is the chief site of absorption in all animals except ruminantsLarge intestine undertake negligible absorptionBut colon absorbs water & electrolytesIn non ruminant herbivores LI absorb products of ceacal fermentation
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17. ABSORPTIVE SURFACESAbsorptive surfaces of SI show foldsFolds of kerckering or Valvulae conniventesIncrease the surface area 3XUpto illeocaecal junction all over these folds are Millions of villiVilli project into lumen of SI 1-8mmVilli increase surface area 10XOn each villus on the luminal side~1000 micro villiIncrease the surface area by 20XTotal increase in surface area is ~1000XTotal surface area in adult man is ~250m2> than the area of tennis court
18. VILLI IN THE SMALL INTESTINEMost important structural elements in absorptionSmooth muscles in wallContractions –tonic & PendularHelp in absorptionMeisnners plexus, sympathetic NS & Villikinin
19. ROUTES OF ABSORPTIONExtremely well developed blood and lymphatic supply in the small intestineAbsorption takes place into blood and also lymphSubstances absorbed into bloodWaterInorganic saltsAmino acidsMonosaccharidesGlycerolShort chain fatty acidsSubstances absorbed into lymphGlyceridesLongchain fatty acidsProteins - Immunoglobulins in collastrumcholesterol
20. MECHANISMS OF ABSORPTIONActive TransportDiffusionSolvent DragWhen a solvent is absorbed by physical forcesIt drags the dissolved substances along
21. ABSORPTION IN THE SMALL INTESTINEAbsorption of waterEntirely by diffusionAccording to laws of osmosiswhen chyme is dilute water is absorbedwhen chyme is concentrated water flows from plasma into chymeThus water absorption in intestine is “isoosmatic absorption”
22. Absorption Of Sodium~1/5 of sodim in the body is absorbed/24hOnly 0.5% of sodium in GI secretions is lost in fecesDiarrhea – lethal sodium loss may occurSodium Absorption is also important in the absorption of sugars and amino acidsAbsorption mechanisms similar to renal tubulesActive absorption from lateral and basal boarders‘passive absorption from brush boarderCounter transport with potassium and hydrogen alsoAldosterone could enhance sodium absorption esp. in the colon.ABSORPTION IN THE SMALL INTESTINE
23. ABSORPTION IN THE SMALL INTESTINEAbsorption of ChlorideIn the upper part – rapid diffusion due to electrochemical gradientFollows absorption of sodium
24. ABSORPTION IN THE SMALL INTESTINEAbsorption of bicarbonateLarge amounts secreted in pancreatic and bile secretionsAbsorbed as carbon dioxide in a fashion similar to that in renal tubules
25. Interstitial fluid Lumen of SIEnterocyteNaNaNaKPATKNaNaKSATNaNaHHSATNaHHSATNaNaHCO3ClClHCO3H2CO3H2O+CO2CO2+H2OH2CO3HCO3HCO3ClClClCl
26. ABSORPTION IN THE SMALL INTESTINEAbsorption of calcium Actively absorbed in duodenumControlled to meet exactly the body needsPTH and vitamin D enhance absorptionCT decreases absorption
27. ABSORPTION IN THE SMALL INTESTINEFe+++Fe++H+SAT+ HFe++Fe++PAT + TransferrinEnterocyteHepatocyteFe++ + ApoferritinFerritinAbsorption of Iron
28. ABSORPTION IN THE SMALL INTESTINEAbosrption of potassium, magnesium & phosphateActively abosrbedMonovalent ions are easily absorbed in large quantitiesBivalent ions are absorbed with difficulty
29. ABSORPTION IN THE SMALL INTESTINEAbsorption of carbohydratesAbsorbed mostly as monosaccharidesGlucose - 80% Glactose and fructose 20% Small quantity of disaccharides also absorbedAll mono saccharides absorbed activelySecondary active trasnport with sodiumFurstose is absorbed by facilitated diffusionTherefore frusctose absorption is only 50% of glucose or Galactose absorption
30. ABSORPTION IN THE SMALL INTESTINEAbsorption of ProteinsMostly absorbed as di-, tri-peptides & AAsMechansim is sodium co-transportFive different types of amino acid and peptide carrier molecules are found in enterocytesTo transport different types of AAs and peptidesSome free amino acids are absorbed by facilitated diffusion
31. ABSORPTION IN THE SMALL INTESTINEAbsorption of Fats
32. ABSORPTION IN THE LARGE INTESTINEMostly water and elelctrolytes are absorbed in the proximal half of colonProximal colon is called “absorbing colon”Sodium and chloride are actively absorbedWater follows osmotic gradient so createdDistal half of colon stores undigested ingesta Called ‘storing colon”
33. Digestion In the PigDiet is essentially plant originUndergoes fermentation in stomach and LIHAUSTRAE
34. PERISTALSIS IN THE GIT OF PIGPeristalsis in stomach develops during feedingbut does not propel food into intestineInstead causes stratification of ingestaTop most is a layer of gasThen a layer of liquidSolid material at the bottomStomach is quiescent for a while after feeding Resumes normal peristalsis subsequentlyRapid movement of chyme from duodenumIngesta are found in ileum within 1-2h of feeding Pass into ceacum for microbial fermentationGasliquidsolid
35. SALIVA AND GASTRIC SECRETIONS IN PIGSaliva has a-amylaseInitiates carbohydrate digestion during masticationGastric juice secretion Continuous under ad libidum feedingMost of it takes place during gastric phaseGastrin stimulates gastric secretionsGastric secretion has high proteolytic activitypH 2.0 – indicates large acid secretion
36. PANCREATIC SECRETION IN PIGAlkaline & rich in enzymesHas proteolytic, lipolytic and amylolytic enzymesVagal control is more important in Pig than in dogLiver and Bile play roles similar to those in the dog
37. FERMENTATIVE DIGESTION IN PIGTakes place in ceacumVFA are producedColon absorbs VFAVFA provide 25% of energy requirements
38. DIGESTION IN THE HORSE(Extremely Large)
39. PERISTALSIS IN THE GIT OF HORSEPowerful peristaltic contractions in the stomachOccur during feedingPropel the ingesta rapidly into small and then large intestineThis helps microbial fermentation in caecumStomach is relatively quiscent after the eating stopsMilk moves slowly from stomachMare milk is rich in fatCauses the release of GIP
40. SALIVA AND GASTRIC SECRETIONS IN HORSESalivaThin water saliva in copious amountsDuring masticationGastric secretionsStomach is relatively small2/5th lined by stratified squamous epitheliumTherefore gastric secretions are small in volumeAcid secretion is continuous during long hours of feedingGastric secretions depend on the nature of ingestaOatas – hydrochloric acid is secretedHay diet causes secretion of organic acids – lactic acid, butyric acid
41. DIGESTION IN THE INTESTINE IN HORSEAlthough movement of ingesta through the intestine is rapidHorses use carbohydrates and proteins better than ruminantsDue to rapid enzymatic break down and absorption in the SIThis is an advantage to energy economy of the speciesTypical array of hepatic, pancreatic and intestinal enzymes as seen in other monogastric animals are present in horses also
42. FERMENTATION IN THE CEACUM OF HORSEMicrobial fermentation takes place in ceacaResults in formation of VFAVFA are absorbed in the colonVFA contribute 25% of the energy requirementsSimilar to Pig
43. DIGESTION IN BIRDS
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45. SPECIAL FEATURES OF DIGESTIVE SYSTEM IN BIRDSMouth & Pharynx are not clearly demarcatedSoft palate and teeth are absentCrop is presentDilatation of esophagus that stores foodCrop is absent in insect eating birdsProventriculus is comparable to glandular stomach of mammalsGizzard is a highly muscular organ for grinding food materialsMuscularity of gizzard depends on the food habitsSmall in grain eating birdsLarge and powerful in fish eating birds
46. SPECIAL FEATURES OF DIGESTIVE SYSTEM IN BIRDSIntestineLong in herbivorous birdsShort in carnivorous birdsSmall IntestineNo demarcations beyond duodenumNumber and size villi are smallNo lacteals in VilliNo Brunners glandsA pair of ceaca a the junction of SI and LILarge in herbivorous birds Small in carnivorous birdsShort Large intestineNo marked areas such as colon and rectumLiverBilobed large structureLeft hepatic duct communicates with duodenumRight hepatic duct communicates with a gall bladder or is transformed into a gall bladderGall bladder is present in chicken, duck and goose but not in pigeon
47. PREHENSION DEGLUTITION AND APPETITE IN BIRDSBeak is the prehensile organInjury to lateral hypothalamusAphagiaIndicates presence of hunger centreInjury to medial hypothalamusHyperphagiaIndicates presence of satiety centreSwallowing occurs by creating a negative pressure by extending the head
48. MOTILITY OF THE GIT IN BIRDSRate of passage of food through the GIT is influenced byConsistency, Hardness, Water contentAge of the bird – rapid in young birdsResidues appear in feces after 4-5h of eatingCrop contractions vary in rhythm and amplitudeBased on nervous state and hungerHungry chicken exhibit 1 contraction/min of proventriculusGizzard exhibits 2-3 contractions /minContractions of gizzardNot influenced by hungerPresence of grit increases the force of contractionsVagus is the principal motor nerve to crop, proventriculus and gizzardSI exhibit peristalsis and segmentationLI exhibit peristalsis and antiperistalsisCeaca undergo peristalsisVagus has no influence on peristalsis
49. SECRETORY ACTIVITY IN THE GIT OF BIRDSAmylase is present in the saliva of birdsBut no digestion takes place as there is no masticationNo digestion in cropRemoval of crop does not inhibit food intake or growthPepsin is secreted in the ProventriculusBut no digestion takes places since pH is too highToo little time is spent by food in the proventriculusMain function of gizzard is grindingNo digestion takes place here although pH is optimal for pepsinGizzardectomy has no adverse influence on digestionPresence of grit increases grinding actionComposition of gastric juiceSimilar to mammals composition is rate dependentQuantity of secretion per unit area is higher than in mammalsCephalic & gastric phases occur but intestinal phase doubtfulPS nerves regulate gastric acid and pepsin secretion
50. DIGESTION IN INTESTINE OF BIRDSDigestion in the stomachUndertaken by enzymes other than pepsinProteolytic enzymes act at relatively higher pHHigher body temperature may increase the pepsin activity although pH is not favourableGIP is absent in birdsPancreatic juiceHas proteolytic, amylolytic and lipolytic enzymesLactase is absent and therefore lactose is poorly digested in birdsTrypsin and chymotrypsin are present Secretin regulates pancreatic secretionBileActivates pancreatic lipaseHelps in absorption of fatsChenodeoxycholic acid is chief bile acidLiver is greatly stimulated by female sex steroidsTherefore proteins, lipids and calcium concentrations are high in plasma of female birdsFermentation of crude fiber occurs to the extent of 18% in ceaca
51. ABSORPTION IN BIRDSCarbohydrates are rapidly absorbed becauseHigh metabolic rate, higher body temperature and short circulation timeSugars are absorbed by SAT as in mammalsDifferent sugars are absorbed at different ratesAmino acidsRapid for L-formsAmino acids with long polar side chains such as Valine, methionine are absorbed rapidlyFatty acids are Absorbed in the last third of intestineInto portal veinsVitamin A is absorbed in duodenumWater is absorbed in the LI