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ANSC 311 - Metabolic Physiology > Lecture 11/12 - Ruminants protein and lipids > Flashcards

Lecture 11/12 - Ruminants protein and lipids Flashcards

1
Q

What does microbial fermentation break down proteins into?

A
  • ammonia which is utilized for microbial protein synthesis
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2
Q

What is microbial protein a primary source of?

A

amino acids absorbed in the small intestine

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3
Q

What does urea recycling provide rumen bacteria with?

A

Nitrogen (low quality protein), which ruminant animals can convert into microbial protein (high quality protein)
- even during starvation

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4
Q

What can ruminant animals convert low quality protein (N) into?

A

Microbial protein = high quality protein

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5
Q

What are 2 cons of ruminant protein digestion?

A

1) Protein is extensively degraded to ammonia, especially with deficiency of energy from CHO fermentation (relying on AA as energy source)

2) Efficiency of N utilization is lower compared to non-ruminant animals
- if a cow is given high quality protein, it is being wasted; could feed a lower quality protein and get the same outcome

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6
Q

5 factors affecting microbial protein synthesis

A
  1. ruminally degradable N (related to amount of protein in the diet)
  2. Energy from CHO fermentation
  3. Quality of ruminally degradable N
    - fiber-digesting bacteria utilize ammonia to make protein whereas start bacteria need aa and peptides to make microbial protein
  4. Passage rate of digesta
    - microbial turnover in the rumen and predation by protozoa can result in excessive loss of microbial protein before it reaches the small intestine
  5. Factors affecting rate of passage
    - feed intake
    - particle size
    - digestibility of fiber
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7
Q

What is ammonia toxicity induced by?

A
  • excessive urea or protein in the diet results in too much ammonia being released; microbes from that forage are not getting enough energy from CHO to replicate and create microbial protein
  • when there is insufficient microbial VFA production ammonia isn’t used up for microbial protein production
  • cellulolytic fermentation
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8
Q

What deaminates urea to ammonia?

A

Ruminal urease

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9
Q

How does cellulolytic fermentation induce ammonia toxicity?

A
  • VFA production rate is lower so less substrate available for protein synthesis
  • rate of microbial division is slower so microbial requirement for protein is less
  • higher ruminal pH favours ruminal absorption of ammonia = impacts CNS
  • toxicity is associated with CNS ammonia intoxication
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10
Q

How can ammonia toxicity induced by cellulolytic fermentation be countered?

A
  • by VFA administration (feeding grain and molasses)
  • lower pH = reduces absorption
  • increases microbial protein synthesis
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11
Q

What is the most important lipid fraction?

A
  • Fatty acids
  • High energy/ some are essential/ impact rumen
  • majority of fatty acids are bound to glycerol as simple or compound lipids
  • majority of FAs are unsaturated
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12
Q

What are most triglycerides degraded into in the rumen?

A
  • FFA and glycerol
  • glycerol ferments in the rumen to VFA
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13
Q

Are fatty acids degraded by ruminal microbial organisms?

A
  • no
  • free fatty acids are extensively biohydrogenated in the rumen (PUFA to saturated FA)
  • saturated fatty acids are absorbed in the duodenum
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14
Q

What are the 3 rumen transformations of lipids?

A
  1. Lipolysis
    - simple (triglyceride) & compound (glycolipid) converted into FFA/NEFA
  2. Biohydrogenation
    - PUFA & MUFA converted into saturated FA
  3. Microbial Lipid Synthesis
    - VFA into branched
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15
Q

How are FA transformed in the rumen?

A
  • intake: highly unsaturated FA
  • outflow: saturated FA

When we consume beef, we are consuming much more saturated fat bc there is this biohydrogenation process where UFA are converted into SFA

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16
Q

What is the goal of biohydrogenation?

A
  • remove double bonds which have antimicrobial properties; if too high in the rumen, they will reduce microbial activity
  • not a direct process, intermediates are formed during the process and some of these are absorbed
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17
Q

What impacts do intermediates of biohydrogenation have?

A
  • can have major effects on animal performance and health
  • trans-10, cis-12 results in suppressed milk fat production; inhibits lipogenesis in the mammary
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18
Q

2 CLA’s to know (intermediates of biohydrogenation)

A

1) cis-9, trans-11
2) trans-10, cis-12 (bad)

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19
Q

Why are humans concerned with rumen lipid metabolism?

A

Affects human health
- meat and milk higher in saturated fat
- bioactive metabolites: anti-carcinogenic, anti-atherogenic, enhance immune system

Affects animal performance

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20
Q

How does rumen lipid metabolism affect animal performance?

A
  • biohydrogenation reduces supply of essential fatty acids (PUFA)- impacts reproductive performance or immune system
  • fatty acid antimicrobial effects (PUFA are antimicrobial so have to monitor how many we give since they will impact microbial ability to ferment and make SCFA)
  • produces bioactive metabolites
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21
Q

What are the major fatty acids consumed in dairy cows?

A
  • any cis isomers (from plants)
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22
Q

What increases FFA in rumen contents?

A

lipolysis

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23
Q

What is the best substrate for the synthesis of CLA in the rumen?

A

essential fatty acids

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24
Q

Microbiota

A

the ecological community of commensal, symbiotic, and pathogenic microorganisms that literally share our body space

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25
Q

What are the most abundant rumen microbes?

A

bacteria>archaea>protozoa>fungi>bacteriophages

26
Q

Why are mammals “superorganisms”?

A

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

27
Q

How were bacterial traditionally classified versus how are they classified now?

A

Traditional
- morphology
- energy source
- fermentation end-products

New
- molecular characterization

28
Q

How do we study the population of microbes?

A
  • hard to culture since there are so many bacteria
  • DNA sequence can tell us who they are and what they do
  • Ribosomal RNA gene is used as a phylogenetic marker bc of its genetic stability and composition of conserved and variable regions
29
Q

What are the main fxns of microbes?

A

1) Provide nutrients
- SCFA and microbial protein
2) Detoxify the diet

30
Q

What are most GI bacteria?

A
  • obligate anaerobes; bc there is not very much O2 in the rumen
31
Q

Do bacteria have different fermentative capabilities?

A

YES
- ex. cellulolytic, hemicellulolytic

32
Q

What are the growth requirements and end products of cellulolytic and hemicellulolytic bacteria?

A

Growth requirements
-pH 6-7
-NH3 (for protein synthesis)

End products
-acetic and butyric acid
-CO2, H2

33
Q

Example of amylolytic bacteria?

A

Streptococcus bovis
- present in low numbers when on forage, or after adaptation to grain diets
- bloom in response to rapid infusion of starch aka produces a lot of lactic acid when we change to a high concentrate diet
- ferments starch to lactic acid, resulting in lactic acidosis

34
Q

What microbe causes lactic acidosis?

A

Streptococcus bovis

35
Q

What is lactic acidosis?

A
  • lactic acid accumulation in the rumen
36
Q

What causes lactic acidosis?

A
  • overfeeding or quick change to high concentrate diet
  • associated with a bloom of amylolytic bacteria such as Streptococcus bovis, which produce lactate
  • once pH drops acid tolerant bacteria take over
37
Q

Why is lactic acid accumulation in the rumen bad? What happens?

A
  • lactic acid in the rumen draws water from the circulation into the rumen causing dehydration
  • results in lysis of gram-negative bacteria = inflammation of rumen wall
38
Q

How can an animal with lactic acidosis be cured?

A

By a rumen transplant from a healthy animal

39
Q

How can acidosis be prevented?

A
  1. introduce concentrate slowly (microbes have time to adapt) and don’t overfeed concentrate
    - other amylolytic bacteria have time to compete with strept bovis and make propionate instead of lactate
  2. rumen microbial population will adapt to high concentrate diets
    - bacteria and protozoa capable of UTILIZING lactate increase in number
  3. target the culprits (streptococcus bovis)
40
Q

What are the fermentation end products of amylolytic bacteria other than Streptococcus bovis?

A
  • acetic acid
  • propionic acid
  • butyric acid
  • CO2
41
Q

What do acid-utilizing bacteria turn lactate into?

A

Fermentation endproducts
- acetic acid
- propionic acid
- valeric acid
- caproic acid

42
Q

Proteolytic bacteria

A
  • only use protein as their sole energy source
43
Q

Lipolytic bacteria

A
  • hydrolyze triglycerides, phospholipids, galactolipids, sulfolipids
44
Q
  1. What are the 2 classes of archaea?
A
  1. free-living
  2. associated with protozoa
45
Q

What are the 2 negative effects of archaea?

A
  1. energy waste
  2. greenhouse gas
46
Q

Rumen fungi

A
  • more prevalent on grasses than legumes
  • important in fiber digestion
47
Q

What does frothy bloat prevent?

A
  • recognition of fluid/foam in cardia prevent eructation
48
Q

What is legume bloat?

A
  • rapid release of proteins results in rapid production of gas by bacteria leading to froth
49
Q

What is feedlot bloat?

A
  • due to dextran slime generated by amylolytic bacteria
50
Q

How can frothy bloat be prevented?

A
  • use antifoaming agents or ionophores that reduce gas production
51
Q

Nitrite toxicity

A
  • excess nitrates accumulate in plants when they are stressed; drought or hot dry winds put forage under water stress
  • bacteria in rumen normally reduce nitrate to nitrite then ammonia; dependent on hydrogen availability
  • due to excess nitrate (and not enough H), nitrite binds to hemoglobin preventing it from carrying O2
  • if the increase in nitrates is gradual the rumen bacteria will adapt and remove it
52
Q

Why are protozoa beneficial?

A

All protozoa store soluble CHOs (glucose) as an amylopectin-like storage polysaccharide
- for protozoa, this maintains a constant energy source
- for the animal, this stabilizes fermentation
- animal would be more prone to acidosis w/o protozoa competing for glucose (CHO) coming in

53
Q

How do protozoa reduce efficiency of protein use?

A

Protozoa engulf and lyse bacteria which contributes to rumen protein turnover reducing efficiency of protein use and increase rumen NH3

54
Q

Advantages of protozoa

A
  1. increased cellulose digestion
  2. slower fermentation of starch and sugars
  3. greater VFA production
  4. increased transport on conjugated linoleic acid and trans-11 fatty acid to duodenum and meat and milk
55
Q

Are protozoa necessary?

A

No!
- have advantages and disadvantages

56
Q

What are the 7 net effects of defaunation (removing protozoa)?

A
  1. increase daily gains due to increased protein efficiency
  2. improved feed efficiency
  3. decreased cellulose digestion
  4. increased total and microbial protein flow to the duodenum
  5. decreased pH on high concentrate diets, but increased pH on high
  6. increased production of propionic acid and decreased production of butyric acid
    - shifting balance of SCFA
    - propionic acid is more efficient
  7. increased rumen volume and liquid outflow rate
57
Q

What are 4 ways the rumen microbes can be manipulated?

A
  1. diet
  2. probiotics
  3. antibiotics
  4. protozoa elimination
58
Q

How can diet manipulate the rumen microbes?

A

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

High concentrate = low pH
- increase amylolytic bacteria
- reduce methanogens and protozoa = less greenhouse gases

59
Q

How can antibiotics manipulate rumen microbes?

A
  • ionophores such as monensin are the most commonly used; creates pores in membranes of gram + bacteria
  • inhibit methane production, proteolysis and AA degradation = overall improves animal efficiency
  • increase propionate
60
Q

How can eliminating protozoa manipulate rumen microbes?

A
  • reduces protein degradation
61
Q

Results of feeding ionophores

A
  • increased propionate
  • reduced protein degradation
  • reduced deamination
  • reduced methane production
  • reduced lactate production
62
Q

What is the composition of microbes predictive of?

A
  • how efficient an animal is

ANSC 311 - Metabolic Physiology (17 decks)

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