Animal nutrition - ruminant digestion Flashcards
ruminal papillae absorb what volatile fatty acids?
acetic acid
propionic acid
butyric acid
characteristics of the reticulum (4)
2nd compartment
has a honey comb structure
separates feed particles and is involved in rumination
sharp foreign bodies collect here (hardware disease)
characteristics of omasum (4)
3rd compartment
muscular omasal “leaves”
reduces the size of particles
primarily absorption of water
(+Mg and VFAs that have surpassed the rumen)
abomasum pH & function (4)
Reduces chyme pH 6.0 → 2.0
– denatures proteins
– kills bacteria and pathogens
– dissolves minerals
– pepsin (chymosin, lipase to smaller extents)
describe Calf milk digestion shortly
Milk is transported via the oesophageal groove directly to the omasum and abomasum.
In the abomasum the milk coagulates by the action of chymosin, and is digested by cathepsin (same as monogastric animals).
microflora develops in calves at
at six months of age
In calves the rumen and reticulum develop after they start to eat solid feed, like starter and hay.
Saliva amount on average for a dairy cow and for sheep
– dairy cow 80-100 l/day
– sheep 10 l/day
Rumen pH?
And temp?
between (5.5) 6.0-7.0 (7.5)
– because of the large amount of saliva, which contains NaH2CO3 (sodium bicarbonate or soda)
– … temperature is 38-42°C
“The normal pH of grass-fed ruminants is 6-7. A pH value of 5.5-6 is seen in cattle on high-grain diets or pasture-fed cattle with early lactic acidosis. pH values less than 5.5 are virtually pathognomonic for lactic acidosis”
The rumen contains three fractions
– gases (top)
– solid fraction (mat) in the middle
– liquid fraction, in the bottom
fractionation takes place, despite the fact that there is a constant mechanical mixing of the rumen contents
rumen-reticulum contracts how much/how often
1.6 to 1.7 times per minute
rumination ? h per day
rumination 10…12 h per day
Ruminal microflora consists of what (3-6)
bacteria, protozoa, fungi,
but also archaea, bacteriophages and yeasts
describe Ruminal Bacteria (5)
– more than 200 species + several sub-species
– 99.5% anaerobes
– the species composition depends on the feed ration
– hydrolyses the dead protozoans
– concentration is 10^9…10^10 cells in 1 ml, i.e. 50…60 (90)% of the total weight of the rumen is microbial
Cellulolytic bacteria break down
cellulose into cellubiose (acetic acid)
Hemicellulose and pectin into oligosaccharides by the same, appropriate degrading bacteria.
Amylolytic bacteria break down starch into?
into maltose and dextrins (propionic acid)
Reminder:
Starch is a polysaccharide which smallest units are glucose.
Maltose is a disaccharide which consists of two glucose units joined by glycosidic bonds.
Dextrins are mixtures of polymers of D-glucose units linked by α-1,4 or α-1,6 glycosidic bonds.
Starch normally contains about 20–30% amylose and 70–80% amylopectin.
Amylose is a polysaccharide made of α-D-glucose units, bonded to each other through α glycosidic bonds.
Amylopectin is a water-insoluble polysaccharide and highly branched polymer of α-glucose units found in plants.
Saccharolytic bacteria convert what into what
mono-, di- and oligosaccharides (sugars) into VFAs (butyric acid)
Lactate-utilising bacteria convert
lactic acid into propionic acid
acetic acid is produced from/by what in the rumen?
Cellulolytic bacteria break cellulose into cellubiose finally producing acetic acid.
The primary product of rumen fermentation is acetic acid.
Cellobiose consists of two molecules of glucose that are linked by a β–(1,4′) glycosidic bond. Cellobiose thus differs from maltose by its configuration at the glycosidic bond.
propionic acid is produced from/by what in the rumen?
Amylolytic bacteria break down starch into maltose and dextrins finally producing propionic acid.
butyric acid is produced from/by what in the rumen?
Saccharolytic bacteria convert mono-, di- and oligosaccharides (sugars) into voltaile fatty acids such as butyric acid.
optimal pH for cellulolytic bacteria
digest fibre at a pH of 6.0 - 6.5
optimal pH for amylolytic bacteria
digest starch at a pH of 5.5 - 6.0
they produce lactate which is utilized by lactic-acid-consuming bacteria which turn it into propionic acid
optimal pH for saccharolytic bacteria
digest sugars at a pH of 5.0 - 5.5
Lipolytic bacteria split
triglycerides into glycerol and fatty acids
Methanogenic bacteria produce what from what
methane from CO2 and hydrogen
Proteolytic and deaminating bacteria hydrolyse
proteins into amino acids and deaminates them into NH3 and carbon chains
hydrolysing bacteria convert urea and biuret into
NH3 and CO2
Biuret is the compound formed by the condensation of two molecules of urea.
“a condensation reaction is a type of chemical reaction in which two molecules are combined to form a single molecule, usually with the loss of a small molecule such as water. If water is lost, the reaction is also known as a dehydration synthesis.”
Ruminal protozoa
–… known > 100 species, 20 are present in any given animal
–… are large (20-200 microns) unicellular organisms
–… concentration is 10^5…10^6 cells in 1 ml
– abundance of protozoa depends on the ration (rumen pH) die in even slightly low pH
–… cannot live in the rumen without bacteria, but bacteria can live without protozoa
Ruminal fungi
– 12 species known
▪ incl. anaerobic yeasts
– their abundance is low
– feed on the cellulose, but also on starch and pectin
– produce extracellular proteases
▪ produce necessary ammonia for cellulolytic bacteria
– the end-products of fermentation are formate, acetate, succinate, lactate, ethanol, CO2, and H2
Ruminant ration consists largely of various carbohydrates (70…80% of energy) such as (4)
– cellulose
– hemicellulose
– STARCH
– water soluble carbohydrates -> SUGARS
▪ monosaccharides (glucose, fructose)
▪ disaccharides (sucrose, maltose, lactose)
▪ oligosaccharides (mainly fructans)
All carbohydrates with one exception are subject to
rumen microbial digestion
but not lignin (which is technically not a carb but is included in fiber group and lumped in with insolulble carbs)
cellulolytic bacteria and fungi attach to the
structural carbohydrates, and hydrolyse them
amylolytic and saccharolytic bacteria attach to
the soluble feed particles, and hydrolyse them
Breakdown of carbohydrates in the rumen can conditionally be divided into two stages:
– I stage: the breakdown of complex carbohydrates into simple sugars by microbial enzymes takes place in the ruminal environment
– II stage: the conversion of simple sugars into volatile fatty acids (VFAs) takes place during microbial intracellular metabolism
uronic acid
Uronic acid pathway is an alternative oxidative pathway for glucose metabolism. It catalyzes the conversion of glucose to glucuronic acid, ascorbic acid, and pentoses.
Uronic acids or alduronic acids are a class of sugar acids with both carbonyl and carboxylic acid functional groups. They are sugars in which the hydroxyl group furthest from the carbonyl group has been oxidized to a carboxylic acid.
xylose
is one of the most abundant carbohydrates on the earth, second only to glucose.
This abundant pentose sugar, along with arabinose, makes up a majority of the hemicellulose backbone as arabinoxylan in the cell walls of cereal grains fed to for exmaple, pigs
Xylose is classified as a monosaccharide of the aldopentose type, which means that it contains five carbon atoms and includes an aldehyde functional group. It is derived from hemicellulose, one of the main constituents of biomass.
cellobiose
Cellobiose consists of two molecules of glucose that are linked by a β–(1,4′) glycosidic bond. Cellobiose is a disaccharide. It is classified as a reducing sugar.
Cellulose is a non-reducing sugar whereas cellobiose is a reducing sugar. Cellulose is a polysaccharide whereas cellobiose is a disaccharide.
Isomaltose
Isomaltose is a disaccharide similar to maltose, but with a α-(1-6)-linkage instead of the α-(1-4)-linkage. Both of the sugars are dimers of glucose.
e.g. Pancreatic α-amylase digests saccharides, forming more maltose and isomaltose.
stage I of rumen digestion end-products
simple sugars are produced, mainly glucose, but also xylose, fructose etc.
Fate of simple sugars in the bacterial cell
(II stage, first part of two)
Sugars entering into the bacterial cell are subjected to glycolysis.
Glycolysis consists of two stages:
– anaerobic phase
phase, takes place in cell cytosol via the Embden–Meyerhof–Parnas glycolytic pathway, glucose is converted into pyruvate
– aerobic phase
when pyruvate is transported from cytosol into the mitochondria and oxidized in the Krebs cycle to acetyl-CoA -> produces CO2+H2O
▪ NB! this phase does not occur in the rumen microbes (no O2)
In complete hydrolysis of 1 molecule of glucose, how many ATP are produced
produces 38 ATP molecules
NB! Decay of glucose in the anaerobic stage produces 4 molecules
of ATP, while the total “energy yield„ for microbes is only 2 molecules of ATP. Not very efficient.
Pyruvate conversion into VFA (II stage, second part)
acetic acid from acetyl phosphate
butyric acid from acetyl CoA
propionic acid via two pathways: lactate or succinate dependent on feed type
carbon number in main VFAs
– acetic acid- C2
– propionic acid- C3
– butyric acid- C4
deamination of amino acids in teh rumen, also produce VFA in small amounts:
– proline → valeric acid
– isoleucine → 2-methyl butyric acid
– leucine → 3-methyl butyric acid
– etc.
a hexose is
a hexose is a monosaccharide (simple sugar) with six carbon atoms.
Roughage feeding increases the formation of
acetate and methane
concentrate feeding increases the formation of
propionate, and reduces the proportion of methane
Micro-organisms, living in the adult animal rumen, produce about ? kg of VFAs daily
Micro-organisms, living in the adult animal rumen, produce about 4 kg of VFAs daily
10…20% of VFAs pass to the abomasum and are therefore absorbed in the small intestine
Produced VFAs are absorbed mainly through the rumen wall, but also through the reticulum and omasum walls, by what two mechanims
– passive absorption or
– by disassociated anion transmission
In addition to ruminal carbohydrate digestion, CH digestion also takes place in
the small intestine, as in monogastric animals
amylopectin
is a water-insoluble polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch, the other being amylose.
microbes reaching the abomasum are killed due to the low pH, and are also subject to digestion in the small intestine therefore,
microbial cellular polysaccharides are also energy sources for the host animal, but their role in energy metabolism is negligible
Ruminants receive ?% of their daily energy need in the form of VFAs.
Ruminants receive 90% of their daily energy need in the form of VFAs.
Thus, ruminants are highly dependent on the process of gluconeogenesis (synthesis of glucose from non-saccharolytic compounds; VFAs -> propionate is the most important at 50-60%)
only ?% of the feed carbohydrate energy becomes usable for metabolism by ruminants
only 65% of the feed carbohydrate energy becomes usable for metabolism by ruminants
65% conversion efficiency seems small, but if we consider that humans can directly convert solar energy from the biomass into usable energy at only 5%, this is great!
Main Ruminal gases (5)
– carbon dioxide 40%
– methane 30…40%
– hydrogen 5%
– small and varying proportions of oxygen and nitrogen, which are bound with other gases
- … 30 l produced per hour
- … production is most intense immediately after feeding
Ruminal methane is produced during ? digestion in the rumen
Methane is produced during carbohydrate (roughage) digestion in the rumen.
As methane is a very energy-rich gas the ruminants lose a large amount of energy. About 4.5g of methane is produced for every 100g of digested carbohydrates. The ruminant loses about 7% of its feed energy as methane.
Why are saponins more “dangerous” when wet?
wet forage/ frosty regrowth of clover
saponins are surface active substances
they form stable foam when wet
In aqueous solution, saponin molecules align themselves vertically on the surface with their hydrophobic ends oriented away from the water. This has the effect of reducing the surface tension of the water, causing it to foam.
Different carbohydrate fermentation rates in the rumen.
sugars fastest (but note, sugars don’t really belong in ruminant diets, at least not in large amounts
starch intermediate
cellulose/fiber longest of course
Conversion of energy sources in the rumen
fiber becomes
starch becomes
sugars become
fats become
fiber becomes acetic acid (mostly)
starch becomes proprionic acid
sugars become butyric acid
fats become fatty acids
Crude protein in ruminant feeds can be divided into
– rumen degradable protein (RDP)
– rumen undegradable protein (RUP)
rumen degradable protein (RDP) is
▪ non-protein nitrogen (NPN) compounds
▪ actual protein
rumen undegradable protein (RUP) is
▪ partly protein
▪ protein bound with lignin, i.e. indigestible protein
Hydrolysis of dietary protein in the rumen
Crude protein fraction divided into protein and non-protein nitrogen.
Protein is hydrolyzed to polypeptides and then to amino acids (these steps happen extracellularly).
Deamination of amino acids happens both inside microbes and extracellularly and produces ammonia, CO2 and VFAs.
Non-protein nitrogen is hydrolyzed to ammonia with is an end-product of the rumen.
endogenous Non protein-N compound in the saliva
urea
The main protein hydrolysis product in the
rumen is
ammonia (very few AAs and peptides)
Bacteria use mainly what for their body synthesis?
– ammonia (synthesis of AA –> proteins), but also
– di- and tripeptides and AAs (amylolytic bacteria)
Protozoa can use only what for protein synthesis?
Protozoa can use only AAs and di- and tripeptides, they cannot use ammonia.
Proteolytic activity of rumen microorganisms
is very high. Degradation rate of NPN-componds in the rumen is
very fast –> about 300% in an hour
▪ i.e., in 20 minutes all is degraded
Proteolytic activity of rumen microorganisms
is very high. Degradation rate of protein in the rumen is
much lower than that of NPN-compounds, and some
remains undegraded.
it depends on:
▪ feed type, grasses’ development phase, silage
fermentation intensity, feed production technology, etc.
Microbial protein can cover a dairy cow’s daily protein requirement at a rate of
60%, but can be up to 100%
The dairy cow is capable of producing a maximum of 18-20 kg milk through the use of microbial protein alone.
Microbial protein synthesis depends on
– amount of energy (ATP) available for microorganisms
– amount of protein in the forestomachs (RDP, amino acids, peptides, dead micro-organisms)
– passage rate of the feed in the GI tract
– requirement satisfaction of mineral elements
in general, from the point of view of microbial protein
synthesis, it is not important, which
protein source breaks down into ammonia
From the point of view of microbial protein synthesis the optimal NH3-N content in the rumen fluid is
3…5 mg/100 ml
13% crude protein in 1 kg ration DM ≈ 5 mg NH3-N 100 ml
if the feed outflow from the rumen is slow (fibre-rich ration),
then the availability of nutrients for the micro-organisms is
is also smaller
(increasing intra-ruminal nutrient recycling), which
leads to lower microbial mass formation
flow should be just right
if the feed outflow from the rumen is high (high starch
ration), then there will be
lack of nutrients, especially AA, peptides and branched chain VFA, for microbial use / protein synthesis
flow should be just right
in practical feeding the limiting factor in the synthesis of microbial protein is
energy.
as opposed to the amount of nitrogen sources present though this is indeed the 2nd rate limting factor
Microbial protein synthesis requires a balance between what
energy and protein.
degradable protein to provide nitrogen for microbial protein synthesis &
fermentable carbohydrates for producing ATP energy to conduct the synthesis
As a rule, during feed protein hydrolysis more ammonia is produced than the rumen microbes can use.
Excess ammonia is
absorbed through the rumen wall into the blood.
In the blood the ammonia is bound to amino acids
(glutamine, alanine), and transported to the liver. In the liver the ammonia is transformed in the ornithine cycle into urea.
Some of the urea in the blood is circulated back intoxxx
the saliva and rumen (stabilising the rumen N balance).
Urea concentrations are very strongly correlated
in blood, urine and milk.
Urea is excreted from the body mainly with
urine.
of total urine N, urea-N constitutes about 70-80%
how much urea is excreted into milk?
(2.5-3%) urea
milk urea content shows how efficiently the dietary protein
is being used, i.e. how much is unused and excreted (should
be no more than 300 mg/l)
PBV
protein balance value
(RUP)
Rumen undegradable protein (RUP) is also digested
enzymatically into AAs, after which are absorbed
together (MP + RUP) form what?
MP = microbial protein
forms of metabolisable protein
(AAT -> amino acids truly absorbed in the small intestine)
Ruminants produce more saliva when we feed them with…
A. roughages
B. concentrates
C. roughages and concentrates together
A. roughages
Starch is digested by …
A. saccharolytic bacteria
B. amylolytic bacteria
C. cellulolytic bacteria
B. amylolytic bacteria
(with enzyme amylase starch is digested to amylopectin and amylose)
In the case of a concentrate-rich feed ration, propionic acid is formed in the bacterial cell from pyruvate via …
A. acetyl-CoA
B. acetyl phosphate
C. lactate
D. succinate
C. lactate via concentrates
D. succinate via roughages
In the case of high levels of concentrates in the feed ration in the rumen fluid …
A. the proportion of acetic acid increases and
the proportions of propionic and butyric acid
decrease
B. the proportion of acetic acid decreases and
the proportions of propionic and butyric acid
increase
B. the proportion of acetic acid decreases and
the proportions of propionic and butyric acid
increase
feeding more starch leads to more proprionate and less acetate
Ruminants cover their daily energy need in the form of VFAs at a percentage of …
A. 10%
B. 25%
C. 75%
D. 90%
D. 90%
can be even up to 100%
Of the following starch sources the slowest to digest in the rumen is …
A. barley meal
B. wheat meal
C. oat meal
D. maize meal
D. maize meal
Cellulolytic bacteria preferred pH range in the rumen is …
A. 6.0-6.5
B. 5.5-6.0
C. 5.0-5.5
A. 6.0-6.5
In the case of a roughage rich ration, the …
A. milk yield is higher and produces more milk protein
B. milk yield is lower and produces more milk fat
B. milk yield is lower and produces more milk fat
The protein digestion end-products in the rumen are …
A. peptides
B. amino acids
C. ammonia
D. urea
C. ammonia
The effective degradability of forage crude protein is greatest when it contains …
A. more crude protein and is ensiled
B. less crude protein and is ensiled
C. more crude protein and is not ensiled
D. less crude protein and is not ensiled
A. more crude protein and is ensiled
The efficiency of microbial protein synthesis depends in the first place on the available amount of …
A. sulphur and cobalt for microbes
B. crude protein and its quality for microbes
C. energy for microbes
C. energy for microbes
Protein digestion end-products in the body are …
A. peptides
B. amino acids
C. ammonia
D. urea
D. urea
Most dangerous to animal health is ammonia, which is produced from …
A.the amino acids deaminated during the renewal
of body proteins
B. amino acids absorbed in the small intestine but
not used
C. feed protein degraded in the rumen but unused
C. feed protein degraded in the rumen but unused
In the case of a concentrate-rich ration, the …
A. milk yield is higher and produces more
milk protein
B. milk yield is lower and produces more
milk fat
A. milk yield is higher and produces more milk protein
