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An Sc 311 Midterm 2 > Lecture 12 - Ruminant Microbiology > Flashcards

Lecture 12 - Ruminant Microbiology Flashcards

1
Q

What is the microbiota

A

Ecological community of commensal, symbiotic, and pathogenic microorganisms that share our body space

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2
Q

Most numerous microbe is

A

Bacteria, then archaea

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3
Q

How are mammals “superorganisms”

A

Metabolic capability is a product of our own genetic potential plus that of our inhabitants

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4
Q

There is competition, but also _____________ between bacteria

A

Cross-feeding

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5
Q

How can we classify bacteria

A

Traditionally
- morphology (size, shape, gram)
- energy source
- fermentation endproducts
Modern = molecular characterization

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6
Q

What is typically used as a phylogenetic marker in microbes? Why?

A

Ribosomal rRNA (16S rRNA)
Genetically stable, composition (conserved and variable regions)

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7
Q

Some environments that microbes may live in in the rumen

A

Particle associated, liquid phase, adherent to rumen wall, omasal laminae, or inside other organisms

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8
Q

Functions of microbes

A

Provide nutrients
Detoxify the diet

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9
Q

Most GI bacteria are…

A

Obligate anaerobes

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10
Q

Name the different fermentative capabilities/classes of bacteria (11)

A

Cellulolytic, xylanolytic, amylolytic, dextrinolytic, pectinolytic, proteolytic, lipolytic, methanogenic, amino acid degrading, glycerol utilizing, lactate utilizing

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11
Q

Growth requirements and end products of cellulolytic and hemicellulolytic bacteria

A

Needs: pH 6-7, NH3

End products: acetic and butyric acid, CO2, H2

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12
Q

Common amylolytic bacteria

A

Streptococcus bovis

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13
Q

When does step bovis grow vs not grow

A

Present in low numbers when on forage or after adaptation to grain diet
Bloom in response to rapid infusion of starch

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14
Q

Strep bovis ferments what to what, causing?

A

Starch to lactic acid = lactic acidosis

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15
Q

What is lactic acidosis

A

Lactic acid accumulation in the rumen

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16
Q

What causes lactic acidosis

A

Overfeeding or quick change to high concentrate diet
Bloom of amylolytic bacteria (S. bovis) which produce lactate (lower pH)
pH drop = acid tolerant bacteria take over (Lactobacillus)

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17
Q

In lactic acidosis, when pH drops and acid tolerant bacteria take over, what happens?

A

Draws water from circulation into rumen = dehydration
Lysis of gram-negative bacteria = inflammation of rumen wall

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18
Q

How do we cure an animal with lactic acidosis

A

Rumen transplant from a healthy animal

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19
Q

Ways to prevent acidosis

A
  • introduce concentrate slowly, don’t overfeed (rumen microbes will adapt to concentrate)
  • target culprits (S bovis) w antimicrobial
20
Q

How does the rumen microbial population adapt to high concentrate diets

A

Other amylolytic bacteria will compete with S bovis if increased slowly and they will make something else (e.g. propionate)
Bacteria and protozoa capable of utilizing lactate will increase

21
Q

Growth requirements, fermentation end products of amylolytic bacteria

A

Need: pH 5-6, CO2, NH3, peptides

Endproducts: acetic acid, propionic acid, butyric acid, CO2

22
Q

Acid-utilizing bacteria use… Creating the fermentation end products…

A

Use lactic acid, succinic acid, formic acid

End products are acetate, propionate

23
Q

What do lipolytic bacteria do

A

Hydrolyze triglycerides and phospholipids with lipases

24
Q

What do proteolytic bacteria do

A

Protein as energy source

25
Q

Two classes of archaea **

A
  1. Free living
  2. Associated with protozoa
26
Q

Archaea associated with protozoa produce… What negative effects does this have

A

Produce methane

Energy waste, greenhouse gasses

27
Q

Where are rumen fungi prevalent? Important for what

A

On grasses more than legumes

Important in fiber digestion

28
Q

What is legume bloat

A

Rapid release of proteins results in rapid production of gas by bacteria leading to froth (alfalfa, red and white clover)

29
Q

What is bloat? One cause is… How do we reduce gas production

A

Fluid/foam in cardia prevents eructation

Genetic effect

Use antifoaming agents or ionophores to reduce gas

30
Q

What causes nitrite toxicity

A

Excess nitrates accumulate in plants when they are stressed (droughts, hot dry winds)

31
Q

What do rumen bacteria normally do to nitrate

A

Reduce it to nitrite then ammonia

32
Q

What does nitrite do

A

Nitrite binds to hemoglobin preventing it from carrying oxygen

33
Q

How to prevent nitrite toxicity

A

Increase nitrates gradually, rumen bacteria will adapt and remove it

34
Q

Where is mimosine found? What does it do? Get rid of it by…

A

In tropical legume
Causes goiters/toxicity in ruminants
Degraded by bacteria Syngergistes jonesii

35
Q

Two families of rumen protozoae

A
  1. Isotrichidae (Holotrichs: cilia over entire body
  2. Oligotrichs: cilia in mouth region
36
Q

Characteristics of protozoa (5)*

A

Larger than bacteria
Slower to replicate than bacteria
Do not readily pass in rumen
Store soluble CHO
Engulf and lyse bacteria

37
Q

Holotrichs exhibit…

A

Chemotaxis, move to back of rumen when animals are eating, settle in ventral/cranial sacs

38
Q

Why do protozoa store CHO as amylopectin-like storage polysaccharides

A

Maintains constant energy source, stabilizes fermentation (prevents acidosis) in ruminant

39
Q

Fermentation end products of holotrichs vs oligotrichs

A

Holo: acetate, propionate, lactate, H2

Oligo: CO2, H2, acetate, butyrate

40
Q

N requirements of protozoa

A

Do not use NH3 (non-protein nitrogen)
Actively proteolytic

41
Q

Advantages and disadvantages of protozoa

A

Adv: cellulose digestion, slower fermentation of starch, greater VFA production
Dis: reduced efficiency of protein use and increased rumen NH3 due to rumen protein turnover. CH4 production

42
Q

Effects of defaunation

A

Increased daily gain, feed efficiency, microbial protein flow to duodenum, production of propionate

Decreased cellulose digestion, pH on high concentrate diets, production of butyrate

43
Q

What is defaunation

A

Killing protozoa

44
Q

How do high forage vs high concentrate diets affect rumen microbe population

A

High forage = high pH, increase cellulolytic bacteria, methanogens and protozoa

High concentrate = low pH, increase amylolytic bacteria, reduce methanogens and protozoa

45
Q

Results of feeding ionophores

A

Increased propionate

Reduced protein degradation, deamination, methane production, lactate production

An Sc 311 Midterm 2 (6 decks)

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