exam 1 lecture 13 fermentation Flashcards
plants can take sunlight and turn it into ____ which is stored as polymers as ___
glucose
cellulose (polysaccharide)
hemicellulose (polysaccharide)
cellulose
glucose polysaccharide
lined by Beta 1-4 linkage to form crystalline structure
not easy to breakdown (ligno-cellulose complex)
hemicellulose
strings of pentose and hexose loosely bound to cellulose
cellulose and hemicellulose are surrounded by ___
lignin
not a polysaccharide/carbohydrate but has a phenyl-propane base
protection of cellulose and hemicellulose
Only microbes have the enzymes to unlock covalent linkages (expose) carbohydrates followed by ___ - fermentation
hydrolysis
Colonization by microbes in the digestive tract becomes essential to exploit the ___ capacity of microbes
fermentative
Microbes derive energy and nutrients during fermentation for their ___
growth
___ mutual benefit between herbivorous host and microbes
symbiosis
birds transfer microorganism to their young by ___
regurgitating food
suitable conditions for fermentative digestion
Reservoir to house microbes in the digestive tract
Anaerobic environment (no oxygen allows for transfer of electrons)
pH range slightly acid to neutral ((>5.3) 6.0 to 7.0)
Passage rates are slow
Utilization of by-products and absorption of end products
chemical conditions for fermentative digestion
pH ((>5.3)6.0-7.0) slightly acid to neutral
buffering systems
VFAs
Physical conditions for fermentative digestion
reservoir
anaerobic environment (no oxygen) - O2 likes to be electron accepter, without it allows exchange of electrons through oxidation and reduction reactions
___ is a region of GI tract enlarged to store food and allow microbiota to colonize and facilitate fermentation
reservoir
___ are examples of foregut fermenters
Reticulorumen – ruminants
Pseudoruminants- not 4 chambers but 2-3
Marsupials – sacciform and tubiform –microbial colonization
Camels, ilpacas-3 stomach –small reticulum, one big rumen and leading to glandular stomach
hindgut fermenters have modifications to the ___
large intestine
Cecum – Rabbit
Cecum and Colon - Horses
foregut or hindgut reservoir are larger
foregut
hindgut are smaller and mostly used for fermentation of fiber
Access to protein is minimal in rabbits and therefore microbial protein formed in caecum is passed into fecal pellets. This is gold for them and they excrete at night and practice ___
coprophagy (eat feces)
in rabbit/hindgut fermenters, VFA acids formed are absorbed through the ___ epithelium
cecal
why do rabbits eat their poop?
coprophagy
recycle nutrients
where are microbes in a rabbit?
cecum- small so food can’t stay long
where does fermentation occur in horses?
cecum and colon- breakdown of fiber
Caecum is temporary reservoir and colon is the major reservoir
The digestive tract is pretty long and it takes quite some time for the feed to reach cecum and colon and therefore horse has to be constantly fed to provide continuous supply of feed
Pasture/hay is major source of forage – digested in cecum, colon
Protein, starch are digested in small intestine
fermentation in horses produce ___ where fermentation in rabbits produce ___
energy
energy and proteins- needs to be eaten again to absorb protein
•The redox potential is for microbial transactions is ___
negative (Eh = -250 to -450 mv)
oxidation reduction reactions produce H, this is split into protons and electrons, electrons are transferred by cofactors, so that the oxidation reduction reactions happen,
the more negative = more reaction occurs = more digestibility for the animal
•Fermentation produces metabolic ___
hydrogen
what happens to the oxygen introduced in feed and water inside the fermentation chamber?
–Diffuse across rumen and hindgut wall
–Used by facultative anaerobes
more grain in the diet will do what to the redox potential of the reservoir
more grain= easier to ferment = less reactions = more positive
more fiber= harder to ferment = more reactions, more protons and electrons = more negative= more digestibility
more grain in diet will cause the pH to do what?
drop
needs to be 6-7 for microbial growth
how is pH regulated in the fermentative reservoir?
volatile fatty acids from microbial growth try to lower pH make more acidic
buffers (bicarbonate and phosphate) increase pH
try to stay 5.4 for foregut fermenters (cows) and 6.0 for hindgut fermenters (horse)
roles of saliva in ruminants
lubrication
buffering NaHCO3
100-150 liters per day
roles of saliva in hindgut fermentation
moisten and soften food
flow associated with chewing
35-40 liters per day
foregut fermenters feed intake pattern are ___
meal based feeder
–Multiple meals per day (10) total eating time 2 to 3 hours with 7 to 12 hours ruminating
–Foregut fermenters process feed slowly
Equine are trickle feeders because
–16 to 18 hours a day eating to maintain a full stomach and constant flow through GI tract
–Hindgut fermenters can process feed more rapidly – higher passage rates than foregut fermenters
microbes need nitrogen to survive and get it from ___
proteins: urea, ammonia and amino acids
doesn’t want protein nitrogen sources- will have to waste energy breaking it down
do fermenters need fats?
no, microbes can make their own fatty acids. do not need supplementation
excess fat can bind to cell walls of bacteria and inhibit microbial fermentation
foregut fermenters can eat
pastures, grasses, hay, silages and grain
horses/ hind gut fermenters can eat ___
grasses, hay and grain
dietary factors/ nutrients between foregut and hindgut
NPN= non protein nitrogen
why not feed fine food to fermenters
fine foods, too small. pass through without getting fermented
- Passage and degradation–Proportion degraded is a function of
- Kd/(Kd + Kp)
–Kd is a characteristic of the feed
–Kp is a function of body size, feed intake, and physical characteristics of the diet
Kd/(Kd + Kp)
•Passage and degradation
–Kd is a characteristic of the feed
–Kp is a function of body size, feed intake, and physical characteristics of the diet
fiber digestibility is __ in foregut fermenters than hindgut fermenters
higher
where is starch and protein digested in a fermenter?
hindgut= SI and a little in the LI
foregut= most in the rumen, some in the SI and very little in the large bowel
In equines, most of dietary starch and CP are digested in the___
small intestine
Both starch and protein are digested in the rumen, starch is also digested in the ___ but lower compared to rumen
lower gut
in a lactating cow vs dry cow, which eats more? and how long will things stay in the rumen?
lactating cows eat more
grains: will move faster in a lactating cow cause she is eating more and the starch can be broken down faster= eats more, digested faster = same amount of starch absorbed?
hay: same time in dry or lactating cow- needs to be fermented, lactation does not affect this speed
passage rate in equine
very fast stomach to cecum→ 3.7 hours
slow: cecum to colon → 1-3 days
foregut fermenter microbiome is made of
bacteria
protozoa
fungi (break down lignin in plants)
archaea (hydrogen foraging)
rumen bacteria form complex enzyme complexes called __ to make it easier to breakdown fiber
cellulosomes
rumen portozoa
50% biomass, but less in number compared to bacteria
ciliates: holotrichs (cilia throughout) and oligotrichs (cilia only at the mouth)
protozoa need help from bacteria and archaea to preform correctly
issues: produce H which can produce methanogens→ methane production. eat bacteria and the material they produce that would produce bacterial protein → nitrogen inefficiency
what would happen in protozoa were removed from rumen
defaunation
bacteria protein produced by bacteria would survive, because protozoa usually eat bacteria
decrease in methane gas
30% decrease in breakdown of fiber
anaerobic fungi in rumen
abundant on fibrous diets
zoospores swim until they grow zoosporangium and attach to fiber/plant particle and relate to carb digestion, grow rhizoids until big enough to release more zoospores and restart cycle
anaerobic fungi are mostly found in what kind of fermenters?
foregut
rumen archaea
scavenge hydrogen
do not contribute to feed fermentation directly
naturally form methane
Methane mitigation strategies can have negative implications on fiber digestion and rumen fermentation
rumen archaea produce methane via three pathways
Hydrogenotrophic methanogens (CO2 + H2)
Methylotrophic methanogens (Methylamides as substrates)
Aceticlastic methanogens (Acetate as substrate)
Methane mitigation strategies can have negative implications on fiber digestion and rumen fermentation
microbes need what to survice
CO2
energy (ATP released during fermentation of carbs and proteins)
nitrogen (ammonia, peptides, amino acids)
minerals
overview of microbial fermentation
cell wall made of cellulose and hemicellulose
break in cellulose, primary fermenter attaches and turns cellulose into oligosaccharides and polysaccharides
these then get broken down even more into acetate, butyrate, propinoate and methane
hindgut fermenters produce acetate instead of methane, why?
smaller container makes less H
acetogen will bind better then methanogens → acetate
___ mitigation strategies can have negative implications on fiber digestion and rumen fermentation
Methane
Herbivorous animals depend on ___to digest plant materials
microbes
Ruminants are ___ fermenters (reticulo-rumen) and hindgut fermenters have modification in ___
foregut
caecum (rabbits) and colon (equines)
A ___ to store food, a pH of ___and anerobic conditions are prerequisites for microbial colonization
reservoir
6-7
Foregut fermenters can digest ___ whereas hindgut fermenters can ferment ___
fiber, starch and protein
good quality fiber
Passage rates are lower in ___ fermenters and higher in ___ fermenters.
foregut
hindgut
___ rates depend on quality of feed, feed intake, feed characteristics, digestion rates and the host
Passage
Microbiota include bacteria, ___ and archaea
protozoa, fungi
Bacteria, fungi and protozoa contribute to cellulose digestion whereas ___ are hydrogen scavengers and exclusively form methane
archaea
The nutrient requirements of microbes are ___, ___ from ammonia or peptides and minerals
ATP released during carbohydrate fermentation
nitrogen
carbs are comprised of
neutral detergent fiber (NDF: cellulose, hemicellulose and lignin)
Non fiber carbohydrates (Pectin, starch and simple sugars)
neutral detergent fibers such as cellulose and hemicellulose is fermented ___
slowly
non fiber carbs such as pectin and starch are fermented ___
quickly
–High forage rations have higher ___ and therefore a controlled rate of fermentation
NDF
neutral detergent fiber (NDF: cellulose, hemicellulose and lignin)
slower fermentation
–High Grain rations contribute to readily available carbohydrates and may lead to ___ fermentation
runaway
starch and pectin (too fast breakdown)
particle size changes fermentation how?
physically effective NDF
too small =too fast
too big = too slow
¾ inch= happy place
needs to facilitate colonization of microbes
there needs to be a balance between ___ and ___ for carb fermentation
•neutral detergent fiber (NDF: cellulose, hemicellulose and lignin) and Non fiber carbohydrates (Pectin, starch and simple sugars)
two stages of cellulose digestion
microbial attachment (colonization)
hydrolysis (enzymatic)
microbial attachment stage of cellulose fermentation
colonization (1st step)
Slow process (Lag phase)- rumination (churning to increase SA and allow growth)
Specific and non-specific binding
hydrolysis/ enzymatic stage of fermentation
2nd stage
a. Endoenzymes
b. Exoenzymes
c. Multi-enzyme complexes
phase 1 of carb breakdown
cellulose, starch, pectin and hemicellulose get broken down and turned into pyruvate
phase II carb breakdown
pyruvate → volatile fatty acids: acetate, propionate, butyrate, CO2 and CH4
Two pathways for propionate production
Dicarboxylic Acid: Forage rations
Acrylate: Grain Rations
Runaway fermentation (high grain) can lead to accumulation of lactate; when lactate production exceeds capacity of acrylate pathway
bacteria fermentation will turn pyruvate into
acetate, formate, H2 and methane
pyruvate → butyrate
two ways: dependent and not dependent on acetate
amount of grain in the diet will determine how fast pyruvate → ___
propionate
increase in volatile fatty acids triggers what?
decrease in pH
tiggers changes in rumen epithelium
most VFA can be absorbed by diffusion, except for ___
butyrate
what happens to acetate when it leaves the rumen
used for oxidation, fat
important as precursor for milk fat
what happens to propionate when it leaves the rumen
used liver → glucose
important as determinant of milk volume
what happens to butyrate when it leaves the rumen
portal vein → beta-OH-butyrate
used for oxidation, fat
stimulates rumen development and papillae length
why is fiber more important for dairy cow
breakdown of fiber → acetate and butyrate → needed for milk fat production
why can beef cows eat more grain then dairy?
grain= propionate- gluconeogenic
fiber = acetate and butyrate= needed for milk fat production
carb digestion in equines is a balance between ___ and ___
forage (fiber) and grains
forages/fiber is fermented in the __ of a horse
cecum and colon
in horses, if grains are fed at a rate beyond the digestive capacity of the small intestine can lead to ___
colic, diarrhea, laminitis and microbial dysbiosis (runaway fermentation)
___produced by carb digestion in horses provided immediate supply of energy.
VFA
•The major reason for microbial fermentation is ___ digestion
fiber
•Fiber carbohydrates are ___ and hemicellulose.
cellulose
•Carbohydrate are fermented to ___ that serve as metabolic fuel. Methane is a by-product of fermentation.
VFA
•____ are the major VFA produced by carb fermentation.
Acetate, propionate and butyrate
High fiber yields ___ and more grain increases ___.
acetate
propionate
Acetate and butyrate are needed for ___ or meat. Propionate is gluconeogenic and correlated with ___.
fatty acid synthesis in milk
milk yield.
•More fiber in the diet is good for microbes and is sufficient for ___
maintenance
Grain is needed to enhance fermentation by increasing molar proportion of ___
propionate.
Excessive grain can lead to ___ formation, drop in pH and causes microbial dysbiosis in both foregut and hindgut fermenters. A balance between fiber and grain is critical for microbial efficiency
lactate
Optimal particle ___ is needed for rumen mat formation and facilitate microbial colonization
size
Microbes need protein in the form of ___ for their growth.
nitrogen
dietary crude protein is broken into two (true protein and NPN) what are these
true protein: can not be broken down by microbes, moves through foregut to be digested later on for animals with higher protein requirments
NPN (non protein nitrogen): needed to feed microbes so they can breakdown other things like fiber
where can microbes get nitrogen
from the diet NPN
from recycled microbial protein (bacteria and protozoa)
endogenous nitrogen: saliva/ dead cells (urea and abraded epithelial cells)
Microbes prefer to utilize ___from ammonia and so all nitrogen sources are converted to ammonia
nitrogen
1st step of protein metabolism is proteolysis, which is ___
convert nitrogen source to ammonia
microbial protein synthesis
The nitrogen source from ammonia forms the building block for microbial protein formation
Need fermentable carbohydrate to supply ATP for microbial protein synthesis
Beneficial to microbes and the host
Microbial protein synthesis occurs in both foregut and hindgut fermenters to support microbial growth
Microbial protein is utilized only in foregut fermenters. It is not absorbed but excreted in hindgut fermenters.
proteins are broken into ammonia by __ and __
bacteria and Protozoa
2nd step of protein synthesis in the rumen
ammonia + energy → microbial cells
Microbial protein synthesis requires N sources (ammonia, peptides, aminoacids) plus a continuous supply of fermentable carbohydrates to supply energy along with growth factors
too little energy to push ammonia to microbical protein can result in
ammonia/urea toxicity
•Protein hydrolysis to ammonia and ammonia capture to microbial protein should go hand in hand to avoid ___.
nitrogen inefficiency
•Synchronization of protein degradation and supply of ___ is important.
fermentable carbohydrate
•Diets are formulated to increase microbial ___ (cheap and best quality) for ruminants
protein
•Microbial protein is of little value to ___fermenters
hindgut
As the rate of passage from the rumen increases there is greater opportunity for ___ to pass out of the rumen.
bacteria
Microbes synthesize their own ___ and there is no need for dietary supplementation
fatty acids
Fatty acids are present as complex ___(galactolipids, phospholipids in forages)
lipids
Microbes cannot tolerate more than __% in dietary lipids
3
Excessive___ can be harmful to microbes and reduce their activity
lipids
To avoid toxicity to microbes, protected ___ are added to ruminant diets to bypass the rumen but available in lower gut
fats
In___ fermenters, lipids are not accessible to microbes
hindgut
•Lipolysis: Complex lipids are hydrolyzed to ___ and glycerol by lipolytic bacteria
free fatty acids
Glycerol is converted to VFA’s; Free fatty acids are ___ in nature
unsaturated
___ : Hydrolyze triglycerides and phospholipids
Anerovibrio lipolytica
___ Hydrolyze galactolipids, phospholipids, and sulfolipids
Butyrvibrio fibrisolvens
___: Conversion of unsaturated FA to saturated FA resulting in the formation of several isomers termed as bioactive fats
Biohydrogenation
cis-9,trans-11 CLA
rumenic acid
Anticarcinogenic
Produced in mammary gland
from vaccenic acid by delta-9 desaturase
75% to 90% of CLA in milk
trans-10,cis-12 CLA
Reduction in body fat
Produced in rumen
Significant reduction in milk fat
in high fiber diet:
linoleic acid → stearic acid
cis9 trans 11
in a high grain diet = more energy linoleic acid → stearic acid
skips steps goes through trans10cis12
- Increasing fermentable carbohydrate at the expense of fiber coupled with higher lipid concentrations triggers alternate pathway
- Alters microbiota leading to production of Trans-10, cis-12 18:2 CLA and trans-10 isomer
•These two isomers inhibit milk fat synthesis in the mammary gland and lead to milk fat depression in dairy cows
ways to mess up fermentative digestion
- Excessive fermentation of starch
- Low pH in rumen or cecum (colon)
- Production of amines
- Production of endotoxins
- Laminitis, rumen parakeratosis, liver abscesses, lung abscesses
- Laminitis and colic
SARA
Sub-acute ruminal acidosis (SARA)
from abrupt change in diet
lactic acid increases, pH drops and fermentation is disturbed
ideal pH for microbs
6.6-6.8 (range 5.5 to 7)
pH > 6 – Fiber digesters; pH< 6 – amylolytic digesters;
pH – 5.5 lactic acid producers
(opportunists) – dysbiosis in the rumen microbiota (SARA, frothy bloat)
___ refers to abdominal pain and is the consequence of all forms of gastrointestinal diseases or problems
Colic
About 10-11% of horses suffer from colic and about ___% cases are fatal – approximately $16 million loses due to colic
11
Dietary factors – high grain, low fiber, ___feed changes, moldy feeds are some major causes for colic
abrupt
Changes in ___ can lead to torsion, twisting, ulcers and uterine pain
microbiota
what happens to microbes during colic
Overall we found that healthy commensals were reduced and bacteria with unknown functions have increased.
best way to reduce colic
- Gradual adaptation to higher grain diets–Over a 1 to 2 weeks to increase concentrate feeding–Highest risk of GI upset in horse is 7 days post-increased grain feeding
- Equine maximal grain rate – 0.4% of BW/meal, usually two meals/day
- Cow – <= 60% of total diet DM as concentrate
