L20&21- Fermenters (#3) Flashcards
Carbohydrate digestion generates__?
Glucose
Glucose fermentation generates?
Volatile Fatty Acids
Methane production allows___ to continue
Glycolysis
VFAs are used to make ____ aka ( __ )
Glucose (gluconeogenesis)
VFA are used to make ____________ as well (other than glucose)
FA
Most forgut fermenters are ________
ruminants
Ruminant stomach is divided into 4 compartments:
- Rumen
- Reticulum
- Omasum
- Abomasum
____ is the largest of the compartments and functions as a fermentation vat
Rumen
Ruminants secrete copious amounts of ____ which is rich in _____ and ______ (needed to buffer acids produced during fermentation, ____ (antifoaming agent), and ___ which helps supply nitrogent for microbial AA synthesis)*
- Saliva.. bicarbondate and phosphate
- Mucus (antifoaming agent)
- Urea
Contents are mixed by ____ of the rumen pillars and wall- how many per minute?
Contractions- 1-3 contractions per minute
During _____, a bolus of fibrous material is formed at the base of the esophagus and regurgitated so that animal can rechew the dietary fibers*
Rumination
Fermentation products, VFAs, are absorbed from the rumen via _____
Papillae
______ allows the ruminant to expel the volumes of gas generated during fermentation*
Eructation
What is the significance of papillae?*
Increase SA of the rumen
Ruminants are divided into 3 cateogories based on dietary preference- what are they? Also give example animals of each
- Grazers (cattle, sheep, buffalo, etc)
- Browsers (deer, moose, giraffe)
- Intermediate feeders (goats, reindeer, elk, etc)
What are the main differences btwn grazers and browsers?*
GRAZERS: have a large rumen allowing for maximal fiber digestion and requiring long fermentation times- their diet is HIGH in fiber and LOW in easily digested carbs
BROWSERS: have a less developed rumen, with short fermentation times- their diet is HIGH in more soluble, easily digested carbs and LOWER in fiber
What are some major differences between grazers and browsers with respect to RUMEN SIZE?** [+/- too]
Grazer (+): Very large, needed to accommodate high-fiber diet
Browser (-): Smaller, deit is lower in fiber, higher in soluble carbs which are more rapidly digested and fermented
What are some major differences between grazers and browsers with respect to RUMEN PILLARS?** [+/- too]
Grazer (+): Well-developed musculature needed to mix bulky, fibrous diet
Browser (-): Musculature is less well-developed bc of lower-fiber diet
What are some major differences between grazers and browsers with respect to RUMEN PAPILLAE?** [+/- too]
Grazer (-): Less extensive, VFA are produced at a mod pace, so do not need to be rapidly absorbed
Browser (+): Very extensive. Allows for the rapid absorption of VFA resulting from rapidly fermented soluble carbohydrates
What are some major differences between grazers and browsers with respect to OMASUM?** [+/- too]
Grazer (+): Well developed. Omasum keeps undigested fiber from entering abomasum
Browser (-): Less developed. Less fibrous diet
What are some major differences between grazers and browsers with respect to SALIVARY GLANDS?** [+/- too]
Grazer (-): Moderate (cow prod 100-150 L/day)
Browser (+): Well developed (3 to 4 times the amnt of grazer). Saliva buffers the rapidly produced VFA and glands secrete tannin binding proteins. Copious saliva washes easily digested food directly into abomasum
What are some major differences between grazers and browsers with respect to RAFT OR MAT FORMATION?** [+/- too]
Grazer (+): High fiber diet leads to mat formation
Browser (-): Low fiber diet decreases tendency to form mat
What are some major differences between grazers and browsers with respect to FERMENTATION TIME?** [+/- too]
Grazer (+): Very long. Long time needed to digest and ferment the high-fiber diet
Browser (-): Shorter time. Low-fiber, high-soluble carb diet, is fermented more rapidly
What are some major differences between grazers and browsers with respect to BIOHYDROGENATION?** [+/- too]
Grazer (+): Extensive hydrogenation bc of long fermentation time and need to dispose of hydrogens generated during fermentation. Fewer PUFA in body fat of ruminant
Browser (-): Less hydrogenation. Higher cc of PUFA are incorp in body fat
What are some major differences between grazers and browsers with respect to GLUCOSE TRANSPORTERS?** [+/- too]
Grazer (-): Fewer glucose transport proteins in SI
Browser (+): Present. Some readily available carbohydrates (RAC) are swept out of the rumen because of the large volume of saliva and are digested and absorbed in the SI
What are the 2 major categories of carbs in forage?* Describe
- Cell contents or solubles carbs- easily digested and make up a larger percentage of the carbs in the diet of the browser
- Cell wall components- are more resistant to digestion and make up the majority of the carbs in the forage of grazers
_____ is composed of linear chain of glucose with B-1,4 linkages- several chains will aggregate to form microfibrils- what is exclusive about mammalian enzymes with the B-1,4 linkages?
Cellulose
- No mammalian enzymes can hydrolyze it
____ has a random structure with many diff sugards besides glucose such as xylose, manose, etc
Hemicellulose
____ is a branched polysaccharide rich in galacturonic acid which fnctions as a glue to hold neighboring plant cells together
Pectin
____ is highly insoluble phenolic polymer crosslinked to the hemicellulose and pectins. _____(repeat) adds rigidity to the plant cell walls
Lignin
Lignification increase with plant ____ and decreases both _____ and ___ of forage
- Plant age
- Digestibility and palatability of forage
3 types of rumen microorganism (RMO) are?
- Bacteria
- Protozoa
- Fungi
____ are the ultimate specialists
Bacteria
What do protozoa engulf? (3 things)
Fiber fragments, starch granules and fiber-digesting bacteria
Digestion of the plant cell walls is carrid out by a __________ of several bacterial species- what does this mean?
Consortium
- Alone one species would be unable to digest but coming together to form a consortium of several species, they can digest cell wall fiber to glucose
What is termed a “readily available carb” (RAC) in contracst to cellulose and hemicellulose which are NOT easily digested and their glucose is NOT therefore readily available?
Starch
What happens ot the glucose obtained from the digestion of carbs from cattle feed?
Fermented by RMO in 2 steps:
- Primary fermentation
- Secondary fermentation
What is primary fermentation?
Uses glycolysis to convert glucose to pyruvate
What is secondary fermentation?
Converts pyruvate to a variety of VFA mainly (acetate, pripionate, and butyrate and some gases)
What are the endproducts of rumen fermentation*? (4)
- VFA (acetate, propionate, and butyrate)*
- Gases (CO2, CH4, H2, HS)
- Heat of fermentation
- Microbial cell mass (princip source of protein for ruminants)
Fermentation only occurs in absence of ____
Oxygen
In ____ glycolysis, glucose oxidation results in the formation of ATP, NADH, and pyruvate
Aerobic
Methane generation provides the means of removing the hydrogen from ______ and allowing a greater total yield of ATP
NADH
___________ converts formate to methan
Methane-prod bacteria aka methanogens
Menthane production presents a MAJOR LOSS OF _____ for the ruminant
Energy
The quantity of celluose and starch in diet influences the proportion of fermentaion endproducts- aka a _____ molar ratio)
Acetate to propinoate (A:P)
A high-fiber diet prod more ___ than propionate, this ratio is close to the number ____
more acetate than propinoate
A:P close to 3
A high-grain diet has a A:P ratio closer to ________
1
Prpinoate prod is inversely related to methane production, therefore a high-fiber diet would be ______ (higher/ lower)
Higher
Prpinoate prod is inversely related to methane production, therefore a high-grain diet would be ______ (higher/ lower)
Lower
A:P Molar ratio changes with ___
Feed
Acute lactic acidosis can occur when pasture-fed cattle are bourght to feedly and _____
Abruptly started on a high-grain diet
When a pasture-fed ruminant with a primarly fiber-digesting microflora is abruptly given a high-grain diet, the shortage of starch-digesting and sugar-utilizing microflora is overcome by an ___, ___________ lactate-producing bacteria
Opportunistic , fast-growing
Acute Lactic Acidosis: Why does rumen become acidic? (3)*
- Lactate is not as rapidly absorbed from rumen as the VFA (acetate, prop, buty)
- Lactate is stronger acid than VFA (pKa of lactate is 3 versus pKa of 4.8 for acetate)
- Saliva prod decreases on a low-forage, high-grain, diet depriving rumen of a much needed buffer
Acute Lactic Acidosis: Why does lower pH precipitate a downward spiral?
- Growth rate of other RMO slows
- The rumen, unlike abomasum has no mucus to protect itself from this increasingly acidic environment
- Rumen papillae slough off creating breaks in surface
Acute Lactic Acidosis: How can we treat this?
- Gradual shift in diet instead
- Acid rumen can be treated by giving sodium bicarbonate
VFA is used as a fuel for muscle precursors for ____ and for FA synthesis
Gluconeogenesis
VFAs are either ___ or ___
ketogenic or glucogenic
Butyrate is cleaved by ____ to form 2 acetyl-coAs
B-oxid
What are the MITV amino acids used for converting Propinoyl coA to succinyl coA using methylmalonyl Coa?
Methinine
Isoleucine
Threonine
Valine
Pathway of prpinoyl to succinyl coA production requires vitamins (3)?
- Pantothenic acid –> Coeznme A moieties
- Biotin –> propinyl coA carboxylase
- Bit B12–> methylmalonyl CoA mutase
How to cattle meet their needs for vits?
- water-soluble vits are made by RMO
- Fat-soluble vits ADEK are obtained from diet or sun
Ruminants are completely dependent on _____ to meet their glycogen and glucose need
Gluconeogenesis
What is the % contribution of propinoate to glucose production?
70%
What tissues require glucose in cattle?
Brain and RBC
Ruminants’ predom fuel? (2)
- Acetate
2. Metabolism of VFA
Monensin increases ___ and efficiency of feed util by 7.5%
Growth
Explain how the following factors help contribute to the increase in grwoth and feed efficiency seen when using monensin:
- Dec A:P ratio
- Dec methan prod (30%)
- Dec AA catabolism
- Dec A:P ratio = MORE PROPIONATE FOR GLUCOSE PROD
- Dec methan prod (30%) = 10% OF CALORIC VALUE IS LOST AS CH4
- Dec AA catabolism = MORE AA AVAIL FOR PROTEIN SYN
The acetyl coA used in FA synthesis comes from ___ and is generate in the cytosol using ATP citrate lyase
Glucose
NADPH for FA synthesis is supplied by what 2 things? %?
- Malic enzyme (50%)
2. HMP shunt (50%)
De novo FA syn occurs primarily in the ____ of ruminants
AT
The acetyl coa used for FA synthesis comes from 2 of the VFA ___ and ___!! but NOT FROM PROPIONATE OR GLUCOGENIC AA
Acetate and Butyrate
Ruminats lack the ATP=citrate lyase- unable to generate acetyl Coa in teh cytosol and foreced to use acetate made ______
In the rumen
NADPH needed for FA biosyn suppliekd by what 2 things
- Cytoplasmic isocitrate dehydrogenase (ICDH)
2. HMP shunt
The absense of ATP-citrate lyase and the presence of ICDH are signifcant evolutionary changes in ruminants relative to ___
Omnivores
Rumen microorganisms? (4 functions)
- Use dietary lipids as sink for hydrogens
- Digest dietary protein to AA and ammonia
- Recycle urea
- Syn the EAA and water-soluble vits needed by ruminants
Host ruminants does what 2 things?
- Uses RMO to supply their AA needs
2. Detoxifies ammonia generated in the rumen and the liver
The primary function of dietary lipids is to ____? (3 things)
- Supply E
- EFF
- Fat- soluble vitamins
Most of the ______ are digested (hydrolyzed) by lipolytic bacteria in the rumen
Dietary lipids
FA made by host ruminant are similar to those made by other animals- specific to what 4 things?
- Even number C’s
- Linear (not branched)
- All dbl bonds are CIS with a KINK
- Methylene bridges (CH2) separate double bonds
RMO form branched chain fatty acids (BCFA)- what are several characterstics of BCFA
- Made from methylmalonic acid
- Favor due to medium length BCFA
- Form some trasn dbl bonds with no kink
- Prod of conjug dbl bonds
Because of the biohydrogenation phenomenon, ruminants have a high concentraton of _______ C16:0, C18:0, C18:1 - thus meat and milk from ruminants is high in saturate fat
Saturated fats
Ruminal AA either ___ (40%) or used directly for bacterial protein synthesis (60%)
Fermented
NPN in feedstuff are also convereted to ____ by RMO
Ammonia
Generally, cattle can grow, reprod and lactate on a diety with only dietary NPN, however they would do better when given ________
Dietary protein
Urea that is to be recycled reaches the rumen via what 2 things?
- Saliva
2. Diffusion across rumen wall
Urea can only be used under what condition of the rumen?
The rumen has to have plenty of urease producing bacteria
Urea has to be administered how often?
Daily to ensure that bacteria are present
Urea levels are termed ______ aka (BUN)
Blood urea nitrogen
BUN levels are a measure of ________________
Crude protein utilization
If diet is low in crude protein, urea levels are ___
Low
If diet is high in crude protein, the surplus AA are catabolized, increasing levels of ________ and ____ which has to be excreted
Ammonia and urea
Which form is more readily absorbed? (NH4 or NH3)
NH3
Fiber in the rumen has to be digested and fermented to do what?
Make room for next meal
Insufficient lvls of RMO will do what things?
Slow down digestion and fermeantion and decrease rate of passage thru rumen
What 2 things in stomach helps kill RMO?
Pepsin and acid
How many genes coding lysozymes are in the cattle vs human?
Cattle has at least 10 genes (4 expressed in abomasum)
Humans have 1 gene
What are “bypass proteins”?*
Dietary proteins specifically designed to escape fermentation in the rumen and to move on to SI for digestion and absorption
___ is a natural bypass protein because suckling causes esophageal groove to close so milk goes directly to abomasum skipping the rumen
Milk
Excess urea means excess ___ and this wastes energy as its coversion back to urea in the liver requires energy (___ATP/urea)
NH3, 4 ATP per urea
