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2 AM - Growth & Nutrition > Protein & Metabolism in the Rumen > Flashcards

Protein & Metabolism in the Rumen Flashcards

1
Q

What nutrients do different dietary components produce in the small intestine as a result of the ruminant digestion process?

A

Nonprotein N (NPN) > Amino acids
Feed proteins > Volatile fatty acids (VFA) & amino acids
Carbohydrates > VFA & glucose
Fats > Fatty acids & glycerol

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2
Q

What are the 2 main types of protein in milk?

A

Microbial protein
Casein

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3
Q

What type of relationship do ruminants have with ruminal bacteria?

A

Symbiotic

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4
Q

What conditions must be maintained in the rumen to support microbial growth?

A
  1. Temperature (30℃), moisture, pH buffered
  2. Constant supply of nutrients
  3. Continuous removal of by-products of digestion/fermentation (eg, gases (methane), VFA, ammonia)
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5
Q

What process produces the bulk of the energy to ruminants?

A

Fermentation
(over digestion)

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6
Q

Which volatile fatty acids (VFA) are present in the rumen, in order of concentration?

A
  1. Acetate
  2. Propionate
  3. Butyrate
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7
Q

List some characteristics of acetate

A

Milk fat precursor
Lipogenic - stored as fat (via acetyl-CoA)
High fibre diets favour acetate production
Absorbed across the rumen wall intact & converted to acetyl CoA in liver > enters Krebs citric cycle

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8
Q

List some characteristics of propionate

A

Glucose precursor
Gluconeogenic - stored as glycogen
High concentrate diets favour propionate production
20% of propionate converted to lactate during absorption across rumen wall, enters gluconeogenic pathway in liver via phosphoenolpyruvate (PEP)
Remaining propionate passes into liver & converted into glucose via oxaloacetate & PEP intermediates

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9
Q

List some characteristics of butyrate

A

Lipogenic - stored as fat (via acteyl-CoA)
Production less controlled by diet, but slightly favoured on high forage diet - presence of protozoa increases production
Butyrate converted to beta-hydroxybutyrate during absorption across rumen wall & passed into liver > converted into acetyl CoA
Beta-hydroxybutyrate may also be used as an energy source by heart & skeletal muscle

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10
Q

What are 2 reactions that produce methane (CH4)?

A

CO2 + 4H2 -> CH4 +2H2O (CO2 reduction)
CH3COOH -> CO2 + CH4 (acetate decarboxylation)

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11
Q

What type of diet produces less methane (CH4)?

A

Diets low in concentrate (H2 sink)

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12
Q

Why must volatile fatty acids (VFA) be removed from the rumen?
How are they removed?

A

Maintain rumen pH
Too many VFA = acidosis
Passively absorbed across rumen wall

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13
Q

What are the 2 types of protein involved in ruminal digestion?

A

Digestible Microbial True Protein (DMTP)
Undegraded Dietary Protein (UDP)

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14
Q

What are the 2 ways rumen microbes are produced?

A

Non-protein N (NH3) -> microbial protein
Hydrolyse dietary proteins -> peptides/amino acids -> microbial protein

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15
Q

What do Low Fermentable Metabolisable Energy (FME) diets use for energy?

A

Amino acids

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16
Q

What are branched-chain Volatile FatAcids (VFA) utilised from?

A

Amino acids

17
Q

What is valine the precursor for?

A

Isobutyric acid

18
Q

Describe the metabolisable protein system

A
19
Q

What is a key intermediate in nitrogen metabolism?
Why?

A

Ammonia
It regulates the use of dietary nitrogen

20
Q

How does low dietary protein lead to less energy generation?

A
  1. Low dietary protein
  2. Less ammonia
  3. Slow microbial growth
  4. Reduced carbohydrate breakdown
  5. Less energy generation
21
Q

What is a result of rapid degradation of dietary protein or insufficient FME?

A

Increased ammonia levels at rumen level

22
Q

What is the fate of urea?

A

Rumen via saliva, converted to ammonia by bacterial urease (N recycling)
Excreted in urine

23
Q

What is the optimum rumen ammonia concentration?

A

8mMol

24
Q

What %’s of dietary nitrogen from forage ends up retained in thee rumen, in urine or in faeces?

A

Forage = 100%
Retention = 20%
Faeces = 30%
Urine = 50%

25
Q

What factors affect ruminal efficiency of microbial protein synthesis?

A

Form of nitrogen
Balance of supply of energy & nitrogen

26
Q

What is a result of good balance between supply of nitrogen & energy (improved nitrogen utilisation)?

A

Improvements in the efficiency of microbial protein synthesis

27
Q

How do you improve the balance between supply of nitrogen & energy (nitrogen utilisation)?

A

Increase levels of readily available energy
Decrease protein solubility of forage protein

28
Q

What’s the average amount of microbial protein in most foods?

A

200g/kg digested in rumen

29
Q

What’s the average amount of microbial protein in rapidly fermentable foods?

A

260g/kg digested in rumen

30
Q

What’s the average amount of microbial protein in low-fermentable foods?

A

130g/kg digested in rumen

2 AM - Growth & Nutrition (7 decks)

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