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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
Two classes of archaea **
1. Free living 2. Associated with protozoa
26
Archaea associated with protozoa produce... What negative effects does this have
Produce methane Energy waste, greenhouse gasses
27
Where are rumen fungi prevalent? Important for what
On grasses more than legumes Important in fiber digestion
28
What is legume bloat
Rapid release of proteins results in rapid production of gas by bacteria leading to froth (alfalfa, red and white clover)
29
What is bloat? One cause is... How do we reduce gas production
Fluid/foam in cardia prevents eructation Genetic effect Use antifoaming agents or ionophores to reduce gas
30
What causes nitrite toxicity
Excess nitrates accumulate in plants when they are stressed (droughts, hot dry winds)
31
What do rumen bacteria normally do to nitrate
Reduce it to nitrite then ammonia
32
What does nitrite do
Nitrite binds to hemoglobin preventing it from carrying oxygen
33
How to prevent nitrite toxicity
Increase nitrates gradually, rumen bacteria will adapt and remove it
34
Where is mimosine found? What does it do? Get rid of it by...
In tropical legume Causes goiters/toxicity in ruminants Degraded by bacteria Syngergistes jonesii
35
Two families of rumen protozoae
1. Isotrichidae (Holotrichs: cilia over entire body 2. Oligotrichs: cilia in mouth region
36
Characteristics of protozoa (5)*
Larger than bacteria Slower to replicate than bacteria Do not readily pass in rumen Store soluble CHO Engulf and lyse bacteria
37
Holotrichs exhibit...
Chemotaxis, move to back of rumen when animals are eating, settle in ventral/cranial sacs
38
Why do protozoa store CHO as amylopectin-like storage polysaccharides
Maintains constant energy source, stabilizes fermentation (prevents acidosis) in ruminant
39
Fermentation end products of holotrichs vs oligotrichs
Holo: acetate, propionate, lactate, H2 Oligo: CO2, H2, acetate, butyrate
40
N requirements of protozoa
Do not use NH3 (non-protein nitrogen) Actively proteolytic
41
Advantages and disadvantages of protozoa
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
Effects of defaunation
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
What is defaunation
Killing protozoa
44
How do high forage vs high concentrate diets affect rumen microbe population
High forage = high pH, increase cellulolytic bacteria, methanogens and protozoa High concentrate = low pH, increase amylolytic bacteria, reduce methanogens and protozoa
45
Results of feeding ionophores
Increased propionate Reduced protein degradation, deamination, methane production, lactate production

An Sc 311 Midterm 2 (6 decks)

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