Digestion And Nutrition

Updated 2008-11-12 02:15

Table 1

Question Answer
fiber digesters as rate limiterslimit the amount of energy substrates and hydrogen available to other bacteria
protozoa as rate limiterslimit the amount of starch available to starch digesting bacteria
protein metabolising bacteria produceNH3, which is an essential nutrient for fibre digesting bacteria
non-cellulolytic bacteria synthesisethe vitamin cobalamin, which is needed by protozoa and cellulolytic bacteria
Succinate produced by fibrobacter is used asan energy substrate for selenomonas, which produces some of the CO2 for fibrobacter
formate is used asa precursor of methan production by methanogenic archaea
Acetate and butyrate are used asenergy sources by the ruminant
lactate willdrive rumen pH down (buffering system should keep healthy)
If cattle introduced to all grain too quicklyget lactic acid poisoning, laminitis, etc.
Hyperammonia producing bacteriaare gram positive, use amino acids as energy sources
Can make dietary proteins resistant to bacteria byheating, reacting with formaldehyde
Rumen pH is5.5-7, buffered by PO4 and HCO3/H2CO3
Rumen temperature39oC
Osmotic pressure of rumenisotonic
Removal of rumen end productseructation of methane and CO2, absorption through rumen wall, passage to the lower gut
Supply of substrate in the rumenfibrous feed is digested slowly so there is always substrate for microbial metabolism
mixing in the rumenrumen movements cycle digesta around the rumen
Main types of rumen organismsbacteria and archaea, fungi, protozoa
Bacteria and archaea concentrations in rumen10X10E10 per ml
Protozoa concentrations in rumen10X10E5 per ml but bigger, so make up same amount of biomass a bacteria
Fungi concentrations in rumen~8% of rumen microbial mass
WHat percent of bacteria live free in the rumen liquor?30-40
What percent of bacteria are attached to food particles in the rumen?60-70
What percent of bacteria are attached to the rumen wall?1
Most food attached bacteria live in colonies calledconsortia
bacteria attach to substrate bydigging themselves a pit or attaching via a glycocalyx
Animals fed a mostly roughage / pasture diet have which major VFA?Acetate, ~70%
Animals fed a mostly grain diet have which major VFA?Still acetate, but % drops to 50% and dropped % is replaced by propionate
the protozoa ophryscolex will ingest starch granules untilit bursts
what is bad about protozoa?they trap feed nitrogen and reduce flow of feed protein to the abomasum
when the rumen is defaunated, fungireplicate rapidly to occupy the niche vacated by the protozoa
butyrate synthesis is similar tolong chain fatty acid synthesis in mammals
Direct synthesis of propionate is similar toreversal of beta oxidation
Other mechanism of synthesis of propionate similar toreversal of part of TCA cycle
Primaryfermentation is an old term thatbundles together extracellular digestion and the initial metabolism of the products of that digestion to pyruvate (which involves glycolosys and the pentose phosphate pathway, which yield energy)

Table 2

Question Answer
List the fiber digesting ruminant bacteriaFibrobacter succinigenes, ruminococcus flavifaciens, ruminococcus albus, butyrivibrio fibrisolvens
Fibrobacter succinigenes- preferred substratebeta glucans (glucose, starch)
Fibrobacter succinigenes- fermentation productsformate, acetate, succinate
ruminococcus flavifaciens- preferred substratebeta glucans (xylans)
ruminococcus flavifaciens-fermentation productsformate, acetate, succinate
ruminococcus albus-preferred substratecellobiose (xylans)
ruminococcus albus-fermentation productsformate, acetate,
butyrivibrio fibrisolvens- preferred substratexylans (beta glucans)
butyrivibrio fibrisolvens-fermentation productsformate, acetate, butyrate
List the starch digesting ruminant bacteriastreptococcus bovis, prevotella ruminicola, prevotella amylophilus
streptococcus bovis- preferred substratestarch (glucose)
streptococcus bovis- fermentation productslactate
prevotella ruminicola- preferred substrateglucose (xylans, starch)
prevotella ruminicola - fermentation productsformate, acetate, succinate
prevotella amylophilus- preferred substratestarch, sugars
prevotella amylophilus - fermentation productsformate, acetate, propionate, succinate
List the acid utilising bacteriaMegasphaera elsdenii, selenomonas lactylitica
Megasphaera elsdenii- preferred substratelactate (glucose, glycerol)
Megasphaera elsdenii- fermentation productsacetate, propionate, butyrate
selenomonas lactylitica- preferred substratelactate, sugars
selenomonas lactylitica- fermentation productsacetate, propionate, succinate
prevotella ruminicola as a rate limiterdetermines the amounts of dipeptides available to celluloytic bacteria
What bacteria digest protein to oligopeptides?Prevotella ruminicola, Butyrivibrio fibrisolvens, Bacteroidies amylophilus
What bacteria digest oligopeptides to dipeptides?Prevotella ruminicola
What bacteria digest dipeptides to NH4?Megasphaera elsdenii, prevotella ruminicola, butyvibrio fibrisolvens, clostridium aminophilum, clostridium sticklandii, peptostreptococcus anaerobius, eubacterium ruminantium, selenomonas ruminantium and protozoa

Digestive anatomy

Question Answer
lingual tonsilsin the mucosa of the root of the tongue
palatine tonsilslateral wall of the oropharynx
soft palate tonsilsventral surface of the soft palate
pharyngeal tonsilsroof of nasopharynx
tubal tonsilsat the pharyngeal opening of the auditory tube
Temporalis origintemporal fossa
Temporalis insertioncoronoid process of the mandible
masseter originzygomatic arch
masseter insertionmasseteric fossa
lateral pterygoid originlateral sphenoid
lateral pterygoid insertionmedio-ventral to condyle
medial pterygoid originlateral pterygoid, sphenoid, palatine
medial pterygoid insertionmedial to mandible
Styloglossus originstylohoid
Styloglossus functionelevates and retracts
hyoglossus originbasihyoid
hyoglosuss functiondepresses and retracts
genioglossus originmedial surface of mandible
genioglossus functiondepresses, moves rostral and curls
geniohyoid originmandibular symphysis to basihyoid
geniohyoid functionmoves hyoid and tongue rostral
Dog oesophagus- submucus glandswhole length
Dog oesophagus- muscularis externa100% skeletal
Dog oesophagus- thicknessincreases caudally
pig oesophagus- submucus glandscranial half
pig oesophagus- muscularis externa90% skeletal
Pig oesophagus- thicknessincreases caudally
Horse oesophagus- submucus glandsonly near pharynx
Horse oesophagus- muscularis externacranial 66% skeletal
Horse oesophagus- thicknessincreases caudally
Cat oesophagus- submucus glandsonly near pharynx
Cat oesophagus- muscularis externacranial 66% skeletal
Cat oesophagus- thicknessincreases caudally
Ruminant oesophagus- submucus glandsonly near pharynx
Ruminant oesophagus- muscularis externa100% skeletal
Ruminant oesophagus- thicknessdecreases caudally
Dorsal sack of the rumen is firmly attached tocrura of diaphragm and left psoas muscles
Rumen and reticulum merge at theatrium ventriculi
Omasoabomasal opening is flanked bytwo folds of mucosa, the vela abomasica
meissner's plexussubmucosal plexus
auerbach's plexusmyenteric plexus, between outer muscle layers

Major GI hormones

Question Answer
Gastrin- DistributionDistal stomach
Gastrin- Action1o: + stomach acid secretion, 2o:+ stomach motility, trophic effect on stomach epithelium
Gastrin- Release stimulusprotein in stomach, high gastric pH, vagal stimulation
Secretin- DistributionDuodenum
Secretin- Action1o: + pancreatic HCO3, 2o:+ biliary HCO3
Secretin- Release stimulusAcid in duodeum
Cholecystokinin- DistributionDuodenum to ileum
Cholecystokinin- Action1o:+ pancreatic enzymes, 2o:- gastric emptying
Cholecystokinin- Release stimulusProteins and fats in SI
Gastric inhibitory polypeptide- DistributionDuodeum, upper jejunum
Gastric inhibitory polypeptide- Action1o:- gastric motility and secretions, 2o:+ insulin (if sufficient glucose present
Gastric inhibitory polypeptide- Release stimulusCHO and fat in SI
Motilin- DistributionDuodenum, jejunum
Motilin- Action1o:Gut motility between meals, 2o:tone lower oesophageal sphincter
Motilin- Release stimulusACh