Animal nutrition - ruminant digestion

Question 1

ruminal papillae absorb what volatile fatty acids?

Answer 1

acetic acid
propionic acid
butyric acid

Question 2

characteristics of the reticulum (4)

Answer 2

2nd compartment
has a honey comb structure
separates feed particles and is involved in rumination
sharp foreign bodies collect here (hardware disease)

Question 3

characteristics of omasum (4)

Answer 3

3rd compartment
muscular omasal “leaves”
reduces the size of particles
primarily absorption of water
(+Mg and VFAs that have surpassed the rumen)

Question 4

abomasum pH & function (4)

Answer 4

Reduces chyme pH 6.0 → 2.0

– denatures proteins
– kills bacteria and pathogens
– dissolves minerals
– pepsin (chymosin, lipase to smaller extents)

Question 5

describe Calf milk digestion shortly

Answer 5

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).

Question 6

microflora develops in calves at

Answer 6

at six months of age

In calves the rumen and reticulum develop after they start to eat solid feed, like starter and hay.

Question 7

Saliva amount on average for a dairy cow and for sheep

Answer 7

– dairy cow 80-100 l/day

– sheep 10 l/day

Question 8

Rumen pH?
And temp?

Answer 8

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”

Question 9

The rumen contains three fractions

Answer 9

– 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

Question 10

rumen-reticulum contracts how much/how often

Answer 10

1.6 to 1.7 times per minute

Question 11

rumination ? h per day

Answer 11

rumination 10…12 h per day

Question 12

Ruminal microflora consists of what (3-6)

Answer 12

bacteria, protozoa, fungi,
but also archaea, bacteriophages and yeasts

Question 13

describe Ruminal Bacteria (5)

Answer 13

– 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

Question 14

Cellulolytic bacteria break down

Answer 14

cellulose into cellubiose (acetic acid)

Hemicellulose and pectin into oligosaccharides by the same, appropriate degrading bacteria.

Question 15

Amylolytic bacteria break down starch into?

Answer 15

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.

Question 16

Saccharolytic bacteria convert what into what

Answer 16

mono-, di- and oligosaccharides (sugars) into VFAs (butyric acid)

Question 17

Lactate-utilising bacteria convert

Answer 17

lactic acid into propionic acid

Question 18

acetic acid is produced from/by what in the rumen?

Answer 18

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.

Question 19

propionic acid is produced from/by what in the rumen?

Answer 19

Amylolytic bacteria break down starch into maltose and dextrins finally producing propionic acid.

Question 20

butyric acid is produced from/by what in the rumen?

Answer 20

Saccharolytic bacteria convert mono-, di- and oligosaccharides (sugars) into voltaile fatty acids such as butyric acid.

Question 21

optimal pH for cellulolytic bacteria

Answer 21

digest fibre at a pH of 6.0 - 6.5

Question 22

optimal pH for amylolytic bacteria

Answer 22

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

Question 23

optimal pH for saccharolytic bacteria

Answer 23

digest sugars at a pH of 5.0 - 5.5

Question 24

Lipolytic bacteria split

Answer 24

triglycerides into glycerol and fatty acids

Question 25

Methanogenic bacteria produce what from what

Answer 25

methane from CO2 and hydrogen

Question 26

Proteolytic and deaminating bacteria hydrolyse

Answer 26

proteins into amino acids and deaminates them into NH3 and carbon chains

Question 27

hydrolysing bacteria convert urea and biuret into

Answer 27

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."

Question 28

Ruminal protozoa

Answer 28

–... 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

Question 29

Ruminal fungi

Answer 29

– 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

Question 30

Ruminant ration consists largely of various carbohydrates (70...80% of energy) such as (4)

Answer 30

– cellulose – hemicellulose – STARCH – water soluble carbohydrates -> SUGARS ▪ monosaccharides (glucose, fructose) ▪ disaccharides (sucrose, maltose, lactose) ▪ oligosaccharides (mainly fructans)

Question 31

All carbohydrates with one exception are subject to

Answer 31

rumen microbial digestion but not lignin (which is technically not a carb but is included in fiber group and lumped in with insolulble carbs)

Question 32

cellulolytic bacteria and fungi attach to the

Answer 32

structural carbohydrates, and hydrolyse them

Question 33

amylolytic and saccharolytic bacteria attach to

Answer 33

the soluble feed particles, and hydrolyse them

Question 34

Breakdown of carbohydrates in the rumen can conditionally be divided into two stages:

Answer 34

– 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

Question 35

uronic acid

Answer 35

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.

Question 36

xylose

Answer 36

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.

Question 37

cellobiose

Answer 37

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.

Question 37

Isomaltose

Answer 37

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.

Question 38

stage I of rumen digestion end-products

Answer 38

simple sugars are produced, mainly glucose, but also xylose, fructose etc.

Question 39

Fate of simple sugars in the bacterial cell (II stage, first part of two)

Answer 39

Sugars entering into the bacterial cell are subjected to glycolysis.

Question 40

Glycolysis consists of two stages:

Answer 40

– 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)

Question 41

In complete hydrolysis of 1 molecule of glucose, how many ATP are produced

Answer 41

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.

Question 42

Pyruvate conversion into VFA (II stage, second part)

Answer 42

acetic acid from acetyl phosphate butyric acid from acetyl CoA propionic acid via two pathways: lactate or succinate dependent on feed type

Question 43

carbon number in main VFAs

Answer 43

– acetic acid- C2 – propionic acid- C3 – butyric acid- C4

Question 44

deamination of amino acids in teh rumen, also produce VFA in small amounts:

Answer 44

– proline → valeric acid – isoleucine → 2-methyl butyric acid – leucine → 3-methyl butyric acid – etc.

Question 45

a hexose is

Answer 45

a hexose is a monosaccharide (simple sugar) with six carbon atoms.

Question 46

Roughage feeding increases the formation of

Answer 46

acetate and methane

Question 47

concentrate feeding increases the formation of

Answer 47

propionate, and reduces the proportion of methane

Question 48

Micro-organisms, living in the adult animal rumen, produce about ? kg of VFAs daily

Answer 48

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

Question 49

Produced VFAs are absorbed mainly through the rumen wall, but also through the reticulum and omasum walls, by what two mechanims

Answer 49

– passive absorption or – by disassociated anion transmission

Question 50

In addition to ruminal carbohydrate digestion, CH digestion also takes place in

Answer 50

the small intestine, as in monogastric animals

Question 51

amylopectin

Answer 51

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.

Question 52

microbes reaching the abomasum are killed due to the low pH, and are also subject to digestion in the small intestine therefore,

Answer 52

microbial cellular polysaccharides are also energy sources for the host animal, but their role in energy metabolism is negligible

Question 53

Ruminants receive ?% of their daily energy need in the form of VFAs.

Answer 53

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%)

Question 54

only ?% of the feed carbohydrate energy becomes usable for metabolism by ruminants

Answer 54

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!

Question 55

Main Ruminal gases (5)

Answer 55

– 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

Question 56

Ruminal methane is produced during ? digestion in the rumen

Answer 56

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.

Question 57

Why are saponins more "dangerous" when wet? wet forage/ frosty regrowth of clover

Answer 57

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.

Question 58

Different carbohydrate fermentation rates in the rumen.

Answer 58

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

Question 59

Conversion of energy sources in the rumen fiber becomes starch becomes sugars become fats become

Answer 59

fiber becomes acetic acid (mostly) starch becomes proprionic acid sugars become butyric acid fats become fatty acids

Question 60

Crude protein in ruminant feeds can be divided into

Answer 60

– rumen degradable protein (RDP) – rumen undegradable protein (RUP)

Question 61

rumen degradable protein (RDP) is

Answer 61

▪ non-protein nitrogen (NPN) compounds ▪ actual protein

Question 62

rumen undegradable protein (RUP) is

Answer 62

▪ partly protein ▪ protein bound with lignin, i.e. indigestible protein

Question 63

Hydrolysis of dietary protein in the rumen

Answer 63

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.

Question 64

endogenous Non protein-N compound in the saliva

Answer 64

urea

Question 65

The main protein hydrolysis product in the rumen is

Answer 65

ammonia (very few AAs and peptides)

Question 66

Bacteria use mainly what for their body synthesis?

Answer 66

– ammonia (synthesis of AA –> proteins), but also – di- and tripeptides and AAs (amylolytic bacteria)

Question 67

Protozoa can use only what for protein synthesis?

Answer 67

Protozoa can use only AAs and di- and tripeptides, they cannot use ammonia.

Question 68

Proteolytic activity of rumen microorganisms is very high. Degradation rate of NPN-componds in the rumen is

Answer 68

very fast –> about 300% in an hour ▪ i.e., in 20 minutes all is degraded

Question 69

Proteolytic activity of rumen microorganisms is very high. Degradation rate of protein in the rumen is

Answer 69

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.

Question 70

Microbial protein can cover a dairy cow's daily protein requirement at a rate of

Answer 70

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.

Question 71

Microbial protein synthesis depends on

Answer 71

– 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

Question 72

in general, from the point of view of microbial protein synthesis, it is not important, which

Answer 72

protein source breaks down into ammonia

Question 73

From the point of view of microbial protein synthesis the optimal NH3-N content in the rumen fluid is

Answer 73

3...5 mg/100 ml 13% crude protein in 1 kg ration DM ≈ 5 mg NH3-N 100 ml

Question 74

if the feed outflow from the rumen is slow (fibre-rich ration), then the availability of nutrients for the micro-organisms is

Answer 74

is also smaller (increasing intra-ruminal nutrient recycling), which leads to lower microbial mass formation flow should be just right

Question 75

if the feed outflow from the rumen is high (high starch ration), then there will be

Answer 75

lack of nutrients, especially AA, peptides and branched chain VFA, for microbial use / protein synthesis flow should be just right

Question 76

in practical feeding the limiting factor in the synthesis of microbial protein is

Answer 76

energy. as opposed to the amount of nitrogen sources present though this is indeed the 2nd rate limting factor

Question 77

Microbial protein synthesis requires a balance between what

Answer 77

energy and protein. degradable protein to provide nitrogen for microbial protein synthesis & fermentable carbohydrates for producing ATP energy to conduct the synthesis

Question 78

As a rule, during feed protein hydrolysis more ammonia is produced than the rumen microbes can use. Excess ammonia is

Answer 78

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.

Question 79

Some of the urea in the blood is circulated back intoxxx

Answer 79

the saliva and rumen (stabilising the rumen N balance).

Question 80

Urea concentrations are very strongly correlated

Answer 80

in blood, urine and milk.

Question 81

Urea is excreted from the body mainly with

Answer 81

urine. of total urine N, urea-N constitutes about 70-80%

Question 82

how much urea is excreted into milk?

Answer 82

(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)

Question 83

PBV

Answer 83

protein balance value

Question 84

(RUP)

Answer 84

Rumen undegradable protein (RUP) is also digested enzymatically into AAs, after which are absorbed

Question 85

together (MP + RUP) form what? MP = microbial protein

Answer 85

forms of metabolisable protein (AAT -> amino acids truly absorbed in the small intestine)

Question 86

Ruminants produce more saliva when we feed them with... A. roughages B. concentrates C. roughages and concentrates together

Answer 86

A. roughages

Question 87

Starch is digested by ... A. saccharolytic bacteria B. amylolytic bacteria C. cellulolytic bacteria

Answer 87

B. amylolytic bacteria (with enzyme amylase starch is digested to amylopectin and amylose)

Question 88

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

Answer 88

C. lactate via concentrates D. succinate via roughages

Question 89

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

Answer 89

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

Question 90

Ruminants cover their daily energy need in the form of VFAs at a percentage of ... A. 10% B. 25% C. 75% D. 90%

Answer 90

D. 90% can be even up to 100%

Question 91

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

Answer 91

D. maize meal

Question 92

Cellulolytic bacteria preferred pH range in the rumen is ... A. 6.0-6.5 B. 5.5-6.0 C. 5.0-5.5

Answer 92

A. 6.0-6.5

Question 93

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

Answer 93

B. milk yield is lower and produces more milk fat

Question 94

The protein digestion end-products in the rumen are ... A. peptides B. amino acids C. ammonia D. urea

Answer 94

C. ammonia

Question 95

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

Answer 95

A. more crude protein and is ensiled

Question 96

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

Answer 96

C. energy for microbes

Question 97

Protein digestion end-products in the body are ... A. peptides B. amino acids C. ammonia D. urea

Answer 97

D. urea

Question 98

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

Answer 98

C. feed protein degraded in the rumen but unused

Question 99

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

Answer 99

A. milk yield is higher and produces more milk protein