GI 4 Flashcards
What are the functions of the omasum?
Concentrate ingesta (absorb water)
VFA (SCFA) absorption - diffusion
Na and Cl absorption (cotransporter)
HCO3- reabsorbed (antiport with Cl-)
The forestomach of the ruminant is lined with _____________________ epithelium
Stratified squamous epithelium
Microbes used _______ and __________ to synthesize amino acids
Ammonia (NH3) and volatile fatty acids (VFA)
What are the two main mechanisms that VFA are absorbed in the rumen
Ionized- require carrier (HCO3-/Ac-antiport)
Non-ionized - diffuse through apical membrane
What is rumen acidosis ?
Fast-fermentable carbohydrates (starch rich) can lead to increased VFA production –> acids decrease the pH of rumen
VFA have pka of 4.8 => more acid will be in HAc form than Ac-
HAc can diffuse direct through membrane
Less Ac- antiport with HCO3- (less HCO3- to rumen => pH increases)
Acidic pH -> proliferation of lactate-producing bacteria –> lactic acid -> more acidic
What are the layers of the ruminal contents?
Gas
Fiber mat
Intermediate zone
Liquid zone
the ________________center is located in the medulla and receives afferent fibers from mechanoreceptor in the dorsal sac where gas accumulates
Eructation
Horses and rabbits are ___________ fermenters
Hindgut
All the glucose available to ruminants is formed by ________________
Gluconeogenesis
Proprionate is absorbed from the portal blood supply by the _________
Liver
Never enters systemic circulation
What invagination of the wall of the reticulum spans from the cardia to the recticulo-omasal orfice; it diverts milk away from developing rumen, directly into abomasum
Recticular groove (esophageal groove)
How is sodium absorbed in the rumen?
Na+ channel- Apical (electrochemical gradient)
Na/N exchanger -apical
Na/K ATPase- basolaterally
What is the main function of primary contractions of the rumen?
Reduce particle size
What is the fate of short chain peptides in the microbial cell?
Hydrolyzed to amino acids
- > synthesis of microbes protein
- > metabolized to VFA and ammonia
Urea can be recycled to the rumen to produce proteins for the host, what are the two sources of urea?
Deamination of endogenous amino acids -> ammonia
Nitrogen absorbed as ammonia from rumen
Liver turns ammonia back to urea which is returned back to the rumen
How are fats hydrolyzed in the ruminant?
Microbial lipase
Anaerovibrio lipolytica -> triglycerides
Buyrivibrio fibrisovlens -> phospholipid and glycolpids
What can occur in cattle when the eructation mechanism fails ?
Tympanism or bloating
How is magnesium absorbed in the rumen?
Mg2+ channel
Affected by K+ concentrations
How is chloride reabsorbed into the rumen?
Cl-/HCO3- exchanger -apical
Basolateral channel
What are the primary volatile fatty acids
Acetic acid (acetate) Propionic acid (propionate) Butyric acid (butyrate)
Most dietary protein undergoes fermentation in the microbes within the rumen. How does the animal meet its protein needs?
Microbial proteins
Microbes are washed out of the rumen with rumen fluids to the abomasum and small intestine -> digestion of microbes
Other sources
Ammonia, nitrates, and urea synthesized to protein within rumen
What minor component of diary feeds is a major component of fat supplements
Free fatty acids
What enzymes do microorganisms produce for lipid digestion
Lipase and phospholipids
Usually rare in plants, but fats are added to diets to increase energy density
What are the steps of the mixing/primary contractions of the rumen?
Bolus enter rumen to cardia
Biphasic contraction of rumen - weak followed by forceful to push larger particles to dorsal sac
Caudal-moving contraction of dorsal sac pushes ingesta farther back
Cainial-moving contraction of dorsal sac- > mix ingesta and start bacteria fermentation
Smaller particles decant to ventral sac separates big and small material
Ventral sac contraction- smaller particles to over crainial pillar to the crainial sac
Cranial sac contracts -further separates to small and large particles
Recticulum contract, recticulum-omasal orfice relax and small particle go omasum
What minor components of most feeds forms cell membranes of animal cells and the surface of milk fat globules
Phospholipids
How is potassium absorbed in the rumen?
Apical and basolateral channels - high luminal K+ concentration (transepithelial potential difference)
What is legume bloat?
Cattle eat fast growing clover/alfalfa
Gas trapped in plant material and doesnt rise to dorsal sac
Mechanoreceptor do not detect gas
Eructation mechanism fails
What must be controlled to maintain fermentation in the hindgut
Substrate supply Control of pH Osmolarity Anaerobiosis Retain fermentation material Remove wastes
What type of protozoa in the forestomach are _________ and belong to genus _______ and _______________
Ciliated; isotricha or entodinium
How many recticular-rumen contractions occur per minute
1-3
Rate and strength depend on structure of diet
Describe the ruminal environment
Substrate availability : food intake regulates by volume, structure, energy, palatability
Temperature: 0.5 to 1 C above body temp
Fluid: drink water and saliva
pH: 5.5–7
Osmolarity: 260bis>400mOsm/L
What are the substrates required for hindgut fermentation?
Carbohydrates and proteins
What closes the reticular groove, so milk bypasss the rumen and directly enters the abomasum
Reflex
Anticipate suckling and suckling -> CNS -> brainstem -> vagus nerve -> groove contracts forming a tube
A ____________ deficiency can be observed when a ruminants diet is suddenly changed from roughage to concentrate
B1 (thyamin)
What is the predominant motility pattern of the cecum? How does this differ from the ventral colon?
Cecum: Low-amplitude contractions move ingesta from haustra to haustra (mixing)
Ventral colon: haustra segmentation and retropulsive peristalsis (mixing) and propulsive peristalsis (movement)
Rumen microbes intake carbohydrates, protein,and lipids to form ?
Volatile fatty acid
Microbial lipase hydrolyze fats to ?
Glycerol, sugars, and free fatty acids
What is the true stomach in ruminants?
Abomasum
What is the largest compartment of the newborn ruminant stomach?
Abomasum
Enlargement of the forestomach occurs after birth
What volatile fatty acid is the most important precursor for gluconeogenesis of ruminants
Propionate
Will enter Krebs cycle as succinate
________ on the surface of microbes generate peptides
Protease
What are the two mobility patters on the rumen?
Mixing (primary)
Erutation (secondary)
What is required for an amino acid to enter the VFA pathway?
Deamination
amino acid –> NH3 + carbon skeleton
Fatty acids released from fatty acids undergo ____________
Hydrogenation
Unsaturated fatty acid -> saturated fatty acid
Absorbed in the small intestine
What is the product of hindgut fermentation
Volatile fatty acids
Carbohydrates digestion in ruminants takes place mostly in the?
Forestomach
Almost no digestible carbohydrate enters intestine
What is the ratio of VFA in ruminants
Acetic/propionic/butyric acid
High forage (fiber) diet-> 70:20:10
High grain (starch) diets -> 60:30:10
The ratio of acetate is lower in the starch diet but the total about produced is greater than the fiber diet
What type of digestion occurs in the forestomach of ruminants or in the cecum/colon of horses
Fermentative digestion
Digestive enzymes of microbial origin
Glycerol and sugars are formed into ______in the rumen microbes
Volatile fatty acids
How is calcium reabsorbed int he rumen?
Not well understood
Apical- probably Ca/H exchanger
Basolateral - Na/Ca exchanger and Ca ATPase
When cattle do not have enough oxaloacetate or an excessive amount of acetylCoA, often seen in high-producing dairy cattle, what condition develops?
Ruminant ketosis
Acetyl CoA -> acetoacetyl CoA -> ketone bodies (acetoacetate, betahydroxybutyrate, and acetone)
What the the function of secondary contractions of the rumen?
Force gas toward the cranial portion of rumen
Occurs at end of primary contraction cycle
What controls reticulorumen motility
ENS and vagus nerve
Stretch receptors/chemoreceptor-> afferent to brainstem (dorsal vagus nucelus)->vagus nerve
What component of plants, that increase with age and ambient temperature of the plant is not digestible?
Lignin
What major type of lipid is found in cereal grains, oilseeds, animal fats, and byproduct feeds?
Triglycerides
What is an example of symbiosis of the ruminant stomach?
Waste products of one species serve as a substrate for another
Eg
R.albus digests cellulose –> hexose, but not protein
B.rumincola detests protein –>fatty acid and ammonia
R.albus requires ammonia and fatty acid for growth
R.rumincola requires hexose for growth
Microbes can synthesize what vitamins
C, K , B
What enzyme hydrolyzes cellulose, hemicellulose, and pectin?
Cellulase (in the rumen)
Polysaccharide to monosaccharide
What are the main gases produced during rumination?
CO2
Methane
What must occur in the fore stomach for glucose, monosaccharides, and short chain polysaccharides to be absorbed by the animal
Microbe uptake
Glucose- glycolytic pathway -> 2pyruvate, 2NADH, and 2ATP
Anaerobic fermentation digestion to produce volatile fatty acids AKA short chain fatty acid (SCFA)
A ________ deficiency can be observed in cobalt poor solids or with diets too high in grain
B12 (cobalamin)
Most amino acids following deamination can enter directly into the VFA pathway except for?
Branch-chain aa (BCAA)
Eg valine
Leucine
Isoleucine
What major lipid if found in forages?
Glycolipids
What are the secondary contractions of the rumen?
Cranial-moving contraction staring in cardio-dorsal blind sac
Contraction moves toward cardia forcing gas to esophagus
