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Rumen GI- F&F > Carbohydrate Fermentation > Flashcards

Carbohydrate Fermentation Flashcards

1
Q

Carbohydrates energy distribution

A

-make up to 70-80% of typical ration dry matter
-supplies 60-70% of net energy

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2
Q

Carbohydrates

A

-multiple monosaccharides units linked together (glucose, xylose, others)

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3
Q

Carbohydrate categories

A

-structural CHO
-non-structural CHO

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4
Q

Structural CHO

A

-part of the plant cell wall providing support
-includes cellulose and hemicellulose, lignin, pectin

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5
Q

Cellulose

A

-Beta 1-4 glucose linkage
-forms long linear strands arranged in parallel

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6
Q

Hemicellulose

A

-beta 1-4 xylose linkage, and other monosaccharides

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7
Q

Lignin

A

-phenol groups attached to CHO chain
-nearly indigestible

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8
Q

Pectin

A

-alpha/beta 1-4 galacturonan linkage
-can be structural or non-structural
-cements plant cell walls together

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9
Q

Non-structural CHO

A

-energy source for the plant
-includes simple sugars (monosaccharides arides or disaccharides)
-includes starch

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10
Q

Starch

A

-chains of alpha 1-4 glucose linkage
>amylose=no side chains
>amylopectin= side chains (alpha 1,6 glucose linkage)

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11
Q

Fiber

A

-slowly digested structural material
-includes cellulose, hemicellulose, lignin
-essential for the rumen fibrous mat

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12
Q

Neutral detergent fiber (NDF)

A

-cellulose, hemicellulose, lignin
-determines dry matter intake (too high results in decreased intake)
>tells us how much animal can eat (high fiber takes longer to digest so takes up space in rumen for longer)

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13
Q

Acid detergent fiber (ADF)

A

-cellulose and lignin
-determines digestibility
-increased ADF results in decreased digestibility

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14
Q

Non-fiber CHO

A

-includes starches and sugars
-take up less space in the rumen because they are not bulky like fiber so do not inhibit intake
-completely digested by microbes and can also be digested by mammal enzymes

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15
Q

Fiber fermentability vs non fiber fermentability

A

-Non-fiber: rapidly fermentable (4-8% per min)
-Fiber: 3-12% per hour

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16
Q

Starch digestion in rumen

A

-Wheat- 88-90%
-Barley- 86-88%
-Corn- 75-77%
-Oats- 88-91%

17
Q

Starch processing

A

-increases digestibility
>grinding and rolling increases SA
>stream flaking increases SA and results in heat hydrolyses starch which increases digestibility

18
Q

Sheep/goats vs cattle whole grain

A

-sheep and goats can chew whole grain
-cattle cannot

19
Q

Fermentation rate

A

-starches (soluble carbohydrates)= rapid fermentation
-Pectin- takes longer to start, but then fermentation occurs quickly
-Cellulose- when you digest starch, VFAs are produced affecting pH which affects cellulolytic bacteria which decreases cellulose fermentation initially and then it increases gradually

20
Q

Fermentation

A

1.break down polymers (non structural or structural carbohydrates) into glucose by enzymes
2.Glycolysis (glucose into pyruvate)
3.Pyruvate used to form proprionate (can also make acetate and butyrate but not efficiently used)=VFA and ATP

21
Q

How is pyruvate used to make proprionate?

A

**Proprionate is most energy efficient and only one that can be used for gluconeogenesis
1.Succinate pathway (randomizing order of carbons)
2.Lactate pathway (non-randomizing)

22
Q

Microbe environment demands for fermentation

A

-only ferment sugar via glycolysis whereas mammals can use aerobic metabolism

23
Q

VFAs

A

-weak acids
-can be in ionized/dissociated form or non-ionized/undissociated form

24
Q

Acetate

A

-2 carbon
-70-80%
-energy for rumen epithelium and muscle
-also involved in fatty acid synthesis (milk fat)

25
Q

Propionate

A

-3 carbon
-20-30%
-used for gluconeogenesis

26
Q

Butyrate

A

-4 carbon
-10%
-used for ketogenesis by forming beta-hydroxybutyrate

27
Q

Products of fermentation

A

-VFAs used by microbes
>important for amino acid synthesis (protein) and FA synthesis (lipids for membranes)
-other SCFAs
>5 or 6 carbons such as Valerate
>non volatile FA usually in non-ionized form
>normally rapidly utilized by secondary bacteria
-lactate
>stronger acid than VFAs which means they can cause acidosis

28
Q

Proportions of VFAs based on diet

A

-high fiber= increased acetate
-high concentrate= increased propionate and overall greater total VFA production

29
Q

VFA absorption

A

-primarily absorbed through rumen epithelium (smaller proportion in omasum and SI)
>has rumen papillae to increase SA

30
Q

Absorption rate of VFA

A

-proportional to the size of VFA
*Butyrate> Propionate > acetate

31
Q

VFA absorption and pH

A

absorption will increase as pH decreases
-non-ionized (HA) >ionized (A-)
-lower pH shifts more to non-ionized form

32
Q

CO2 diffusion into epithelial cells

A

-carbonic anhydrase to break into HCO3- and H+, which is important for VFAs absorption
-bicarbonate transported into rumen for buffering
-H+ binds with VFA for transport into the blood

33
Q

VFA absorption components

A

-passive VFAs (HA-) diffusion into the cell, bicarbonate diffuses out to help buffer rumen
-voltage gated VFA channel to transport into the blood

34
Q

Lactic acid absorption

A

-small quantities can be absorbed by the rumen but it is very slow (10% of the rate of the VFAs)
>this is because it is a stronger acid. Lactic acid has lower pKa; and is more likely in ionized (A-) form at moderate rumen pH

35
Q

Grain overload

A

-rapid accumulation of lactic acid
-cannot be absorbed until pH drops significantly
-accumulates in rumen and pulls water into the rumen which can lead to dehydration and metabolic acidosis

36
Q

Electrolyte absorption

A

1.Cl moves from rumen into blood
>pulled by electrical gradient (rumen more negative than epithelial cells); moves against concentration gradient
2.Na moves from rumen to blood
>pulled against both electrical and concentration gradient so needs active transport
>also moves with ionized VFAs
3.K moves in both directions with no net difference
4.Water moves with osmolarity towards high solute concentration. Normally from rumen to blood

Rumen GI- F&F (10 decks)

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