Exam 2

Question 1

Is rumen bacteria large?

Answer 1

No, its small! 10^10-10^11 cells/mL ruminal fluid

Question 2

What is the replication time of rumen bacteria?

Answer 2

Generally short replication time. Most 20-60 min (can be 48+ hrs)

Question 3

Cellulolytics are highest on which diet?

Answer 3

Highest number on a high forage diet. Lower numbers on a high starch diet (but still present)

Question 4

What are some prominant Cellulolytic species?

Answer 4

• Ruminococcus albus
• Ruminococcus flavifaciens
• Fibrobacter succinogenes
• Butyrivibrio fibrisolvens

Question 5

What are Cellulolytics responsible for in the rumen?

Answer 5

• primary H producers in the rumen
• symbiosis with methanogens, other H utilizers

Question 6

What do Cellulolytics produce?

Answer 6

Cellulase a membrane-bound enzyme complex of several subsequent enzymes (cellulosome)

Question 7

How does pH effect cellulolytics?

Answer 7

Very sensitive to pH change fiber digestion begins to decrease below pH 6.0 growth severely retarded below 5.5

Question 8

Where doe cellulolytics get their Nitrogen from?

Answer 8

• Ammonia (NH3)
  
  • very limited use of amino acids, peptides

Question 9

Growth of cellulolytics is stimulated by what?

Answer 9

Branched-chain VFA isobutyrate, isovalerate, 2-methylbutyrate

Question 10

What are hemicellulolytics or pectinolytics?

Answer 10

• simple sugar degraders
• Sucrose, maltose, cellobiose, dextrins Increase with high grain, lush pasture
• Most species of bacteria

Question 11

What is the reaction that takes place with hemicellulolytics/pectinolytics?

Answer 11

• HC/Pectin –> Cellobiose + pentoses –> glucose Pentoses released for use by other species

Question 12

Amylolytics increase on what diet?

Answer 12

• Increased #’s on a high starch diet lower #’s but always present on a high forage diet
• Some cellulolytics capable of starch digestion

Question 13

What are some important amylolytic species?

Answer 13

• streptococcus bovis
• prevotella ruminocola
• bacteriodes amylophylus

Question 14

What do amylolytics produce?

Answer 14

Amylase extracellular enzyme activity regulated by pH

Question 15

What do amylolytics such as S. bovis directly produce?

Answer 15

Lactic acid (lactate) etiology of lactic acidosis

Question 16

Where do amylolytics find their source of Nitrogen?

Answer 16

• NH3 and amino acids+peptides
• Max growth requires AA+ peptides
• Require 2/3 of N supply from AA+peptides provision of pre-formed protein vs. NPN

Question 17

What do intermediate acid utilizers use?

Answer 17

Lactate, succinate, and other organic acids

Question 18

What are some important intermediate acid utilizer species?

Answer 18

• Megasphaera elsdenii
• Selenomonas ruminantium

Question 19

What do intermediate acid utilizers play an important role in?

Answer 19

• adaptation to high grain diets
• S bovis produces lactate excess lactate –> lactic acidosis
• M. elsdenii converts lactate to propionate

Question 20

What do proteolytics produce?

Answer 20

• Major NH3 producers in the rumen protein –> peptides –> AA –> NH3 NH3 production greatly exceeds own reqts.
• Use C-skeleton of AA for energy

Question 21

What are some important proteolytic species?

Answer 21

• Peptostreptococcus anerobius
• Clostridium stricklandii
  
  • NH3 production is 10x higher than mixed rumen microbes identification via monesin sensitivity (Strickland)

Question 22

Bacteria use what as an energy source?

Answer 22

Simple sugars no cellulase or amylase rely upon CHO digestion by other species

Question 23

T/F: Methanogens are a true bacteria

Answer 23

False, they are archae

Question 24

T/F: Methanogens need oxygen to survive

Answer 24

False, they are strict anaerobes

Question 25

fWhat do methanogens use from cellulolytics?

Answer 25

Require and use Hydrogen CO2+ 4H2 --\> CH4 +2 H2O

Question 26

What pH are methanogens sensitive to?

Answer 26

Low pH Lower #'s on a high grain diet (pH 5.5-6.0)

Question 27

What is methanogen growth inhibited by?

Answer 27

* monensin methanogens are NOT overtly monensin sensitive * Restricted supply of H * less H produce fewer (fewer Gram +) * Increased utilization of other H sinks

Question 28

Acetogens are direct competitors with what?

Answer 28

* methanogens compete for Hydrogen * lower affinity for H than methanogens * methanogens outcompete acetogens for H manipulate acetogens to reduce methanogenesis

Question 29

Ureolytics produce what?

Answer 29

Urease Urea--\> CO2 +2 NH3 Membrane-bound enzyme

Question 30

Where is there a higher population of ureolytics?

Answer 30

* Rumen wall * play a role in recycling of blood urea to rumen * maintain low intra-ruminal urea concentrations ensures positive concentration gradient for diffuesion

Question 31

Lipolytics produce what?

Answer 31

Lipase extracellular and membrane-bound forms

Question 32

What do lipolytics ferment?

Answer 32

* Glycerold is fermented propionate (energy) * Fatty acids are not fermented in the rumen * Biohydrogenation

Question 33

Biohydrogenation of unsaturated fatty acid by Gram + bacteria is what kind of mechanism?

Answer 33

Detoxification mechanism conformation of cis double bonds in SFA vs. USFA

Question 34

Biohydrogenation of USFA by Gram + bacteria plays what role in the body?

Answer 34

* Role in FA composition of stored body fat * Conjugated Linoleic Acid * Rumenic acid * anticarcinogenic (breast cancer)

Question 35

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ have fewer numbers than bacteria, but up to equal mass. (larger than bacteria)

Answer 35

Protozoa

Question 36

What percentage of microbial Nitrogen in the rumen do Protozoa produce?

Answer 36

20-50% remain resident in rumen attachment to larger particles, rumen wall contribute to intestine N outflow is negligible

Question 37

What are the two general classes of protozoa

Answer 37

* Holotrichs * Endtrodiniomorphs

Question 38

Describe Holotrich Protozoa.

Answer 38

* Low #'s * Large Diameter * Long replication time (38 h+) * Very sensitive to low pH (\<6.0) * Exist mostly on high forage diets

Question 39

Describe Entodiniomorphs

Answer 39

* Highest #'s * smaller diameter * most have shorter replication time (~8hrs) * Tolerant of low pH (can survive \<5.5 for short time) * Survive well on high grain diets

Question 40

Protozoa digest only\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.

Answer 40

Nonstructural CHO do NOT digest fiber (no cellulase) engulph larger feed particles produce high levels of propionate & butyrate

Question 41

Protozoa\_\_\_\_\_\_\_\_\_\_\_\_ starch.

Answer 41

* sequester/store * role in moderating lactic acidosis keeps starch away from amylolytic bacteria

Question 42

Protozoa often engulph too much \_\_\_\_\_\_\_\_\_\_\_.

Answer 42

Starch Overload--\> cell lysis

Question 43

Protozoa have ___________ #'s with high __________ diets.

Answer 43

* Generally lower #'s with high grain diets no holotrichs (pH too low) * Fewer entodiniomorphs

Question 44

Protozoa does not use what as a Nitrogen source?

Answer 44

NH3 require pre-formed protein (AA, peptides) have proteolytic capability can make significant contribution to NH3 pool

Question 45

Protozoa are called miniruminants because\_\_\_?

Answer 45

predation of other microbes engulph bacteria (or smaller protozoa) sometimes called miniruminants cellulolytics survive inside protozoa

Question 46

Though fungi are large, most are smaller than \_\_\_\_\_\_\_

Answer 46

protozoa

Question 47

Fungi have ______ numbers in the rumen and ______ turnover from rumen. They replicate via ______ formation.

Answer 47

Low numbers in the rumen low turnover from rumen replicate via spore formation

Question 48

Fungi digest ______ using \_\_\_\_\_\_\_\_\_\_\_\_. ______ aid in breaking apart strands of fiber which expose cellulose to bacteria.

Answer 48

* Fungi digest cellulose using fungal cellulase. * Hyphae aid in breaking apart strands of fiber to expose cellulose to bacteria.

Question 49

Explain why fungi is low in #'s despite role in fiber digestion.

Answer 49

hard to establish, maintain large population inoculation increases fiber digestibility chronic inoculation required ongoing research focus fungal extracts (cellulase)

Question 50

What are the three types of interactions?

Answer 50

* parasitism (one benefits, other harmed) * commensalism (one benefits, no effect on other) * mutualism (both benefit) * -often increases efficiency of both species * -removal of feedback inhibition

Question 51

Utilization of intermediates/endproducts include

Answer 51

Succinate, lactate, ethanol, formate, H2, CO2 accumulate in pure culture not detected (or very low) in mixed culture

Question 52

When crossfeeding with proteolytics, what are the products of protein breakdown?

Answer 52

* NH3 AA and peptides * C-skeletons of AA * -BCVFA (from BCAA- Val, Ile, Leu) * -Aromatic compounds (from aromatic AA- Phe, Tyr)

Question 53

When crossfeeding with proteolytics, what is utilized by other species?

Answer 53

* NH3 used by cellulolytics, most other species * -synthesis of AA BCVFA, aromatic compounds used by cellulolytics * -synthesis of corresponding BCAA, aromatic AA

Question 54

Protozoal interactions will likely include...

Answer 54

* Engulphing large particles in rumen -bacteria (attached to feed particles "Mini-ruminants" * -cellulolytic bacteria digest cellulose for protozoa * -protozoa digest bacteria * -- use bacteria as a source of AA * --supply NH3, AA/Peptides, BCVFA, etc to other species

Question 55

Nutrient limitations account for what?

Answer 55

* The variation in microbial #'s * -normal eating patterns * -- max populations 2-6 h after feeding * -Rate of CHO fermentation

Question 56

\_\_\_\_\_\_\_\_\_\_\_\_\_ are highly susceptible to nutrient limitations

Answer 56

* Intermediate acid utilizers * Selenomonas ruminantium (ST50= 2.5 h) * Megaspheara elsdenii (ST50= 3-5h)

Question 57

A shift in the fermentation pathway causes?

Answer 57

* A higher ATP yield * -more acetate, less propionate * -can be between or within species

Question 58

Microbes are efficient scavengers of\_\_\_\_?

Answer 58

NH3 low saturation at cell wall

Question 59

What are two methods of Nitrogen incorporation into the cell?

Answer 59

* Glutamine Synthetase * Glutamate Dehydrogenase

Question 60

Describe Glutamin Synthetase.

Answer 60

* High affinity for NH3 * One mole ATP per mole of NH3 fixed * Spend energy incorporating N when NH3 is limiting (high affinity, works at low NH3, requires ATP)

Question 61

Describe Glutamate dehydrogenase

Answer 61

* Low affinity for NH3 * No ATP requirement * Majority of NH3 fixation at higher NH3 (Low affinity, needs high NH3, no ATP required)

Question 62

If there is a change in diet, microbes adapt how?

Answer 62

* most all microbes present at all times (shift in proportion only) * Transition time depends on magnitude of change

Question 63

If you go from a forage diet to a high concentrate diet, what occurs?

Answer 63

* Increased rate of fermentation * -increased VFA concentration = lower pH * Selection against pH sensitive species * -decreased cellulolytics, increased amylolytics * decreased methanogens * general decrease in protozoa * -fewer below 6.0 * --entodiniomorphs can withstand short-term pH below 5.5 * -role in moderating acidosis * engulf starch --\> less lactate * engulf too much starch --\> lysis

Question 64

What is lactic acidosis?

Answer 64

* accumulation of lactate in rumen * insuficient IAU population to utilize lactate * lactate is stronger acid (pH may drop \< 5.0) * low ruminal pH * inhibits ruminal contractions * damage to rumen epithelium --\> liver abscesses * low pH inhibits amylase activity in rumen * scours * high starch content (gray appearance) * intestinal casts (repair of damage to intestinal wall) * wide fluctuation in feed intake * off feed --\> hunger --\> off feed --\> hunger

Question 65

How do you avoid lactic acidosis?

Answer 65

* Need to increase IAU population * S Bovis (20 min) vs. M elsdenii (48 h) * Gradual step up program is required * 3-4 wk adaptation protocol * add s10-20% grain to diet every 3-4 days * allows time for increase in population of M. eldenii to match the rate of lactate production * concerns once adapted * feeding mistakes, weather change, processing * may need to add long forage to diet and readapt

Question 66

What are some ionophore antibiotics (VFD exempt)?

Answer 66

Monensin (Rumensin) \<-- Coban (for poultry) Lasalosid (Bovatec) Laidlomycin (Cattlyst)

Question 67

What is ionophores mechanism of action?

Answer 67

* ion transport channels in cell membrane * increases ion flux across cell membrane * microbe enteres futile ion cycle * available energy expended pumping ions (Na pump) * increased maintenance energy req. * less energy available for growth Ionophores inhibit growth of Gram + bacteria

Question 68

Ionophores may depress ______ digestion

Answer 68

Fiber digestion (short term) major cellulolytics are Gram +

Question 69

Ionophores have a major effect on \_\_\_\_\_\_\_\_\_\_.

Answer 69

Methanogens Secondary effect of less H2 * decreased acetate: propionate ration * increased capture of energy as VFA * improved feed efficiency * selects agains major NH3 producers * increased peptides, AA

Question 70

How do ionophores influence protozoa?

Answer 70

protozoa are monensin sensitive (coccidiostat) Originally used in poultry (coban)

Question 71

How do ionophores influence feed intake?

Answer 71

Decreased total intake, increased eating frequency smaller meals --\> decreased acidosis

Question 72

streptococcus bovis

Answer 72

Amylolytic bacteria

Question 73

selenomonas ruminantium

Answer 73

Intermediate acid-utilizing bacteria

Question 74

ruminococcus flavifaciens

Answer 74

cellulolytic bacteria

Question 75

peptostreptococcus anaerobius

Answer 75

proteolytic bacteria

Question 76

ophryoscolex caudatus

Answer 76

entodiniomorph protozoa

Question 77

methanobacterium ruminantium

Answer 77

methanogen

Question 78

megaspheara elsennii

Answer 78

intermediate acid-utilizing bacteria

Question 79

isotricha intestinalis

Answer 79

Holotrich protozoa

Question 80

fibrobacter succinogenes

Answer 80

cellulolytic bacteria

Question 81

entodinium caudatum

Answer 81

entodiniomorph protozoa

Question 82

dasytricha ruminantium

Answer 82

Holotrich protozoa

Question 83

clostridium stricklandii

Answer 83

proteolytic bacteria

Question 84

butyrivibrio fibrisolvens

Answer 84

cellulolytic bacteria

Question 85

bacteroides amylophylis

Answer 85

amylolytic bacteria

Question 86

anaerovibrio lipolytica

Answer 86

lipolytic bacteria

Question 87

Do ruminal protozoa have the ability to digest cellulose? Explain your answer.

Answer 87

No, they do not have cellulase. However, since they often engulf cellulolytic bacteria who then live inside them like mini-ruminants, they do have some cellulose digestion inside them because of the cellulolytic bacteria

Question 88

Entodiniomorph vs. Holotrich #'s relative to other protozoa (high vs. low) size relative to other protozoa (large vs. small) sensitivity to low pH (tolerant vs. tolerant) typical replication time (in hrs.)

Answer 88

Entodiniomorph: * #'s relative to other protozoa: **high** * size relative to other protozoa: **small** * sensitivity to low pH: **tolerant** * typical replication time: **8 hrs** Holotrich * #'s relative to other protozoa: **low** * size relative to other protozoa: **large** * sensitivity to low pH: **sensitive** * typical replication time: **36 hrs**

Question 89

List and compare two primary enzyme systems used by rumen bacteria for fixing nitrogen. For each enzyme, indicate 1) the optimum relative NH3 concentration required for activity of each enzyme and 2) energy use in the reactions catalyzed by these enzymes.

Answer 89

Microbes us glutamine synthetase and glutamine dehydrogenase to fix NH3. GD requires a higher concentration and microbes prefer to use it because it does require any ATP or cost them any energy. They use GS when NH3 concentrations are low/limited, but it does require ATP.

Question 90

What influences does short-term starvation have on bacterial numbers in the rume. Which bacteria are most susceptible to such nutrient limitations, and why? What changes in cellular metabolism do these microbes make in response to nutrient limitation and how does this influence VFA production in the rumen?

Answer 90

Short term starvation decreases the overall number of microbes in the rumen. Intermediate acid utilizers are most susceptible, because they have a long replication time which makes it hard to build the population back up when some die. To compensate, microbes shift their ferementation pathways to get a higher ATP yield and they produce more acetate than proprionate.

Question 91

Moorella thermoacetica

Answer 91

Acetogen

Question 92

Describe the primary structural difference between gram positive and gram negative bacteria. Which type of bacteria are susceptible to monensin, and how does monensin affect the growth of these susceptible bacteria.

Answer 92

Gram positive bacteria are susceptible to monensin. This is due to only having 2 layers for the monensin to penetrate into the cell and effect ion flow (only one membrane). Monensin uses an ion flow mechanism to kill the bacteria. Using the Na/K pump, monensin pushes more K into the cell forcing the pump to use more ATP to pump Na out of the cell to maintain ion concnetration. This results in lower Na, higher pH and lower substrate utilization inside the cell and lower K and lower ATP inside the cell. This is a futile cycle that leaves too little ATP for the bacteria to reporduce.

Question 93

What role do acetogens play in the rumen? What substrates do these microbes utilize, and what endproduct do they produce? What is the underlying reason why there are few acetogens in the rumen, and why migh higher numbers of these microbes in the rumen be beneficial?

Answer 93

Acetogens utilize H to produce acetate. They have a lower affinity for H than methanogens which is why their numbers are low. They would be more beneficial because they produce acetate rather than methane, which is more efficient.

Question 94

What specific location within the rumen would the majority of ureolytic bacteria be found and why? What enzymes do these microbes produce and what is the role of these microbes in the process of recycling blood urea into the rumen?

Answer 94

Ureolytics are found in the rumen wall because they have closer access to the blood. They take in urea from the blood and bring it into the rumen. Their enzyme urease turns urea into CO2+ NH3, which can be used by other microbes.

Question 95

What effect do ionophors have on both intake patterns and overall feed intake in cattle? How does this effect relate to use of ionophores as a tool to moderate ruminal acidosis and why?

Answer 95

Ionophores decrease feed intake. The presence of monensin triggers the satiety center of the brain, telling them they are full. The cattle eat smaller, more frequent meals, rather than overeating in one sitting. This decreases acidosis because there isn't such a large influx of starch.

Question 96

As a nutritoinist for the feedlot in the previous question, it is alos your duty to train employees of the feedlot on how to recognize and prevent ruminal acidosis. Begin your training program by describing the outward signs/symptoms of acidosis that the employees should be looking for and when and how these assessments should be conducted. In addition, discuss what feeding practices should be followed to prevent acidosis from occuring and your approach to correcting a situation in which a significant number of calves in a pen are exhibiting signs of acidosis.

Answer 96

* Symptoms * grey feces * this is caused by the increased starch levels going through the intestine. The starch is femented in the hind gut and increases VFA's and other products in the large intestine. This increases fecal water content, so the feces will be loose. * Going on/off feed * cattle with acidosis will gorge then go off feed, then gorge again. This occurs because their belly hurts due to a low pH in the rumen which is burning the rumen wall. They feel better once the rumen is empty and are really hungry by that point, so they overeat and the cycle begins again. * Mucous cast * once over acidosis , the cattle will pass a mucous cast. This is the mucous coating that lines the small intestine. It served as a protective barrier against lactic acid, but damage will cause it to pass and rebuild. * Employees should * check daily for symptoms because acidosis will drastically decrease gains and can lead to death * be sure to feed multiple smaller feedings throughout the day to avoid overeating * watch closely as the weather changes. cattle will gorge before storms, typically * be wary of feeding mistakes. Changes will affect the cattle! * If acidosis occurs * offer longstem forage to calves to decrease amylolytic populations, increase pH and improve the health of rumen microbe populations

Question 97

Describe the importance of branched-chain fatty acids to the rumen microbe population. Include in your answer 1) the three most common BCFA 2) how these BCFA are formed and by which class of ruminal microbes and 3) which other class of ruminal microbes requires BCFA for optimal growth and for what purpose

Answer 97

Proteolytics produce BCVFA's by deamination of AA and BCAA. Cellulolytics use BCVFAs to synthesize AAs and BCAA. They reaminate BCVFA to AA and BCAA. This provides AA and BCVFA for utilization by other microbes. The 3 BCVFA are isobuterate, 2 methylbuterate, and isovalerate.

Question 98

Describe the process of biohydrogenation by ruminal microbes. Include in your answer which ruminal microbes perform this biohydrogenation and the underlying reason why they do so.

Answer 98

The rumen microbes prefer SFA to incorperate into their cell membrane for structural intergrity. Gram positive bacteria perform biohydrogenation.

Question 99

Why would it be beneficial to maintain a viable population of protozoa in the rumen of a steer fed a high grain diet? Include in your answer at least two reasons why maintaining that population of protozoa can be difficult when high grain diets are fed.

Answer 99

Protozoa digest starch which would be used by amylolytics. By protozoa using it, less lactic acid is produced. Maintaining the population can be hard because holotrichs have slow replication and are sensitive to pH. Also, protozoa are less likely to over eat starch and go through lysis.

Question 100

Descibe the life cycle (replication process) employed by ruminal fungi. Include in your answer a discussion of how this process influences overall cellulose digestion within the rumen.

Answer 100

Fungi are spore replicators. Zoospores embed in plant material and begin to grow. They root into the plant particle, using a rhizoid. This then branches out which helps break up the plance material, exposing more cellulose. Fungal cellulase is excreated, allowing the fungi to utlilize the cellulose. The fungus grows and reproduces and the cycle continues. Although fungi numbers are relatively low in the rume, they greatly influence cellulose digestion. The breaking up of the plant material exposes more cellulose for cellulolytics to digest.