Physio 2 - Ruminant GI

drraythe's version from 2015-06-09 01:48


Question Answer
Pseudo-ruminant lacks?Omasum
How big can the fermentation vat get?Up to 250L in cattle
4 main strata of the ruminal ingesta? (From top to bottom)Gas cap, plant mat, slurry zone, liquid zone
Most active fermentation is going in what layer of the rumen ingesta?Solid zone
Rumen "lake"/ liquid zone mostly composed of?MOSTLY saliva, also drinking water
What is the potential escape zone? What escapes?Omasal orifice, only small particles & fluid
1st movement of the reticuluo-rumen movements are?Biphasic contraction of retic...during 2nd contraction the omasal orifice dilates & omasum relaxes (suction)
During the 1st R-R movement, where does the ingesta go?Course, light particles to the dorsal sac / small heavy particles & fluid to cranial sac & omasum
What is the 2nd movement of the R-R movement?Reticulum relaxes, cr. sac contracts, cranio-caudal contraction of dorsal sac & dorsal blind sac
Where does the ingesta go during the 2nd R-R movement?Fluid back into retic....coarse, light particles mixed in dorsal rumen....small heavy particles & fluid pressed ventrally
What is the 3rd movement of the R-R movements?Cranio-caudal contraction of ventral sac & ventral blind sac followed by caudo-cranial moving contraction
Where does the ingesta go during the 3rd R-R movement?Sm particles & fluid pressed dorsally & flow back into cr sac/ reticulum...coarse fibers remain in dorsal sac
The R-R movements happen in cycles. How often do they happen? When do they not happen?3 contractions/ 2min depending on coarseness. Only absent in deep sleep (a little > 1 a minute)
Passage rates depend on digestibility. Which is least digestible, which is most? About how long for the least digestible?Least is coarse fibers (72 hrs), most is lush grass/concentrates
What are B-cycle movements aka?Ructus/ 2⁰ contraction/ eructation contraction
When does ructus happen?After 2-3 A-cycles, depending on rate of gas formation
Describe ructus contraction movements?Ca-Cr contraction of rumen push gas cap forward to cardia → activated cardia receptors → sphincter relax → gas into eso → antiperistalsis waves to move gas orally → inhalation/exhalation
Inhibition of ructus → what happens?Accumulate gas → BLOAT → pressure on thoracic organs → circ failure
Main causes of bloat?Lateral recumbency during anesthesia, obstruction of eso, ruminal stasis
Possible Tx for bloat?Dont feed up to 72 hrs, if anesthesia → keep head up so gas can escape
Nerve responsible for ruminal stuff?Vagus
What controls reticuloruminal motility?Vagal REFLEX (no spontaneous activity)
4 things monitored by vagal reflex?(1) Receptors in mouth/forestomach/stomach/SI
(2) Vagal (Sensory) afferent fibers
(3) Motility center in medulla oblongata
(4) Vagal (motor) efferent fibers
The intrinsic system (in terms of vagal) can modulate _, but CANT _Can modulate activity, CANT maintain a coordinated motility pattern
MAIN receptors of R-R motility? (2)(1) Stretch receptors
(2) Chemoreceptors
What are stretch receptors of the rumen stimulated by? Inhibited by?Stim by mild to mod distension of R-R wall (↑ motility & rumination)....inhibited by severe distension
What do chemo-receptors of the rumen detect & do in response?Detect pH (norm=5.5-6.8), if falls <5 it depresses motility to slow fermentation
Motility center has NO spontaneous activity & needs to be driven by the receptors...what happens if the receptors are damaged?Ruminal stasis (vagal indigestion) TRP (traumatic reticuloperitonitis)
What is TRP?Traumatic reticuloperitonitis → HARDWARE DZ
Why do ruminants eject/ruminate (remasticate)?Helps break up coarse fibers, ↑ surface area for microbes. Stim saliva secretion to stabilize rumen enviro
What is the ruminant circadian rhythm?Periods of feeding alternate w/ periods of rumination
The rumination reflex is controlled by? Stim by? React to?VAGAL REFLEX which involves the rumination center / medulla oblongata. Stim by mechano-receptors, React to fiber coarseness & degree of filling
When does the rumination cycle occur in relation to the other cycle?Immediately before an A-cycle
What is an indicator of the ruminant’s well-being?The rumination cycle
How does the physiology of ejection/rumination occur?Extra contraction of the reticulum → cardia relaxes → glottis closes → inspiration movement sucks bolus into esophagus → antiperistaltic waves propells bolus to mouth → water pressed out/swallowed, rechewing
What is the reticular groove formed by?The muscular lips b/t the cardia & omasal orifice
What is the reticular groove reflex controlled by/stimulated by? What does it do?It is a vagal reflex, stimulated by suckling (oral receptors) & by anticipation. The muscular lips of the groove contact & twist to form a closed tube.
What is the purpose of the reticular groove reflex?It allows the milk to reach the abomasum directly w/out being fermented in forestomach. (Avoid loss of proteins to microbes & fermentation of lactose to lactic acid, a mucosal irritant).
What can the reticular groove reflex be triggered by in adults? Why would you use this?Can be activated by ADH in thirst, or ORAL APPLICATION of copper salts / sodium salts...used to protect oral drugs from being fermented
How does food enter the omasum?Ingesta passes through reticulomasal orifice during 2ND CONTRACTION OF RETICULUM (pushing action) (This is still part of the 1st reticuloruminal movement) while omasum relaxes (sucking action) (fluid & particles then enter)
How is the "pumping action" of the omasum carried out?Orifice closes briefly, canal contracts, pressing ingesta b/t leaves, then body contracts, pressing ingesta forward into abomasum.
Retention time in omasum?1/2-3 hrs
What is the motility of the omasum controlled by?Intrinsic nervous system
Fxns of omasum are? (3)(1) Pass food from reticulum to abomasum
(2) Absorption of residual VFAs, water & bicarb
(3) Some grinding due to partly cornified epithelium
What can movement of the omasum be impaired by?TRP (depends on correct stratification of food in the reticulum)
What does the host provide for the microbes in their symbiotic relationship?Shelter, food/water, removes waste products, maintains a stable environment (temp, pH, osmolality, ↓ O2)
What do the microbes provide for the host in their symbiotic relationship?Leaves energy-rich waste products for host which it couldnt use in original form & nutrients through synthesis (VITAMINS, proteins)
How do bacteria colonize the rumen to being w/?After birth, through contact w/ environment
BACTERIA in the rumen have what kind of O2 needs?Anaerobic
How do BACTERIA in the rumen get grouped?By fxn (cellulolytic, amylolytic, methanogenic, etc)
Three main groups of microbes in rumen?Bacteria, protozoa, fungi
What is necessary for colonization via protozoa?Need contact w/ other ruminants
How much of the microbial biomass is protozoa?Half
What do the protozoa provide? Are they essential for host’s survival?Essential protein, but they aren’t essential for survival
How do microbes access the plant matter in the rumen?Need to enter through pores or cut ends for fermentation to begin
What part of the microbe contains the enzymes (to get into plant material)?It’s part of their outer membrane
After microbes start to break down starch (rare) & cellulose/hemicellulose/pectin (have the beta-linkages) what is the product?Fructose 1-6-bis-P (phosphate)
How is Fructose 1-6-bis-P transformed into the next step, what is the (main) product?Microbes absorb fructose 1-6-bis-P bact get 2 ATP + NADH2 w/ product PYRUVATE
Can the microbes do an electron transport chain?No, that would require O2 & they’re in an anaerobic environment
What is pyruvate broken down into the MOST? What are the waste products of this & why do we care about the products?ACETATE (60-70%) w/ end products of ATP & 2 CO2 which the bacteria use (ATP for energy & CO2 to regenerate stuff/ make methane, so methane+CO2= need ructus)
What are the other 2 products (not acetate) of microbes breaking down pyruvate? What do the end products do?Propionate & butyrate, whose end products allow (NADH2 → NAD)
What happens after pyruvate is converted into lactate? Possible probs?Usually it is further converted into propionate & acetate, however if it stays at lactate it can be a problem
How is the methane formed?CO2 is converted into it
What is the method/cycle the microbes use to create energy & products?Glucolytic cycle
Does the host benefit from the ATP products of the glucolytic paths?Nope, they’re just waiting for the end products
What are the things the host is waiting for to absorb for its use?The acetate, propionate & butyrate (VFAs)
What is the host's main protein source?The microbes themselves
How much of the host's energy requirements are supplied by the VFAs? (%)**60-80% !!
How does the microbe get ATP in the fermentation process?Fermentation yields ATP via main acetate pathway
What can the bacteria use the ATP produced in the acetate pathway to do?Regenerate reduced co-factors (NADH2 → NAD+) via propionate & butyrate to keep pathways open
What is the waste product of the acetate path?CO2
How & why is CO2 converted to methane? Downside?Methanogenic bacteria convert it, it helps regenerate more cofactors. However, methane is a big energy loss :(
How are VFAs absorbed? What does it require? (2 ways)Absorbed as free acids (has H attached to it) = lipophilic, which requires a ↓ rumen pH (~4.8) (cell exchanges an inside hydrogen for an outside sodium to keep absorbing cell's pH neutral.) OR in ionized form & probably exchanges a bicarb for it (with bicarb/VFA exchanger)
Healthy rumen pH?5.5-6.8 (slightly acidic)
What is involved in buffering the pH of the rumen?↑ in VFAs will ↓ pH → saliva & bicarb secretion via rumen wall neutralize
Which is fermented faster, soluble carbs or structural carbs?Soluble.
Why would you want to feed more soluble carbs? Why not?Yes bc more energy so good production system, No bc causes rapid acid ↑ challenges buffering ability, will suppress bact populations = possible acidosis
What are proteins fermented into?By microbes into NH3 & VFAs
How do microbes synthesize proteins?They need a carbon skeleton (VFAs), a nitrogen source & ATP.
What are sources of nitrogen for microbes? (2)(1) Ammonia from proteolysis (LIMITED in natural diet)
(2) Non-protein nitrogen (NPN) aka urea, nitrates
Essentially how do microbes make proteins?Reverse process of breaking down proteins
What is the bottle-neck point of the microbes?Getting enough nitrogen.
How are NPNs (non-protein nitrogen) supplied? (2)(1) Dietary supplementation (ppl feed them chicken urine/feces → UREA) (2) Naturally via rumeno-hepatic nitrogen re-cycling
What is urea & where is it formed? From what?Waste product of protein catabolism, formed in the LIVER from catabolism of endogenous amino acids (mm tissue) & ammonia absorption from rumen & Lg intestines
What happens if ruminal NH3 conc is ↓?Urea is secreted directly or via saliva into rumen for bact. growth...this is RUMINO-HEPATIC nitrogen recycling
What is rumino-hepatic nitrogen recycling?Urea is secreted directly or via saliva into rumen for bact. growth
What happens if ruminal NH3 is ↑?Urea is excreted via kidneys
What organ is most sensitive to urea (ammonia)?Brain
What do ruminants depend on to cover their protein requirements?Digesting microbes flushed from rumen into rest of GI
How does a cow get rumen acidosis?Imbalance b/t VFA production & buffering capacity, eg sudden ingestion of highly digestible carbs (↑ VFA, ↓ salivation+rumination, ↓ pH)
What is the pH of "no return" for acidosis?pH of <5.5
What happens when the pH <5.5? (pathology of it)VFAs go from ionic to free state, are then readily absorbed, intracellular pH is at 7 so those free acids disassociate back to ionic form, Na/H exchanger is overloaded, intracellular pH drops, that inhibits the Na/K pump, more H & Na accumulate, water total, edema & ↓ pH kills cell
What happens to the lactate process when pH <5.5?↓ pH favors lactate producers & inhibits fermentation to VFAs, lactic acid not absorbed well, pH continues to drop, osmolality ↑, water enters rumen.
Final results of acidosis?Damage to epithelium, barrier fxn & absorption impaired, systemic infxns, metabolic acidosis, ruminal stasis (motility of rumen run by vagus, which is driven by receptors which are driven by pH (inhibited in acidity) & distension (overextension is inhibited) ), dehydration, renal failure, shock, death
What do you find upon meat inspection w/ CHRONIC acidosis?Liver abscesses (rumenitis → bact → filtered by liver) & highly keratinized epithelium of foregut
How to prevent chronic acidosis?More structural carbs & COARSE concentrates
How to treat ACUTE acidosis?Remove content as soon as you can, give buffer per os, ↑ level antibiotics, transfer rumen fluid from healthy animal to the sick one
What’s special about the HOATZIN?Eats leaves! Like a browsing herbivore. Its the "ruminant of the avian world" its crop is HUGE (can impair flying) & is used for fermenting. "Stink birds" bc of manure smell they have. Chicks have 2 claws on wings