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NUTRITION > 13 – Rumen CHO, Fibre, Fermentation > Flashcards

13 – Rumen CHO, Fibre, Fermentation Flashcards

1
Q

How much glucose does a lactating dairy cow need per day (liver)?

A
  • 5kg/day
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2
Q

CHO

A
  • Make up 70-80% of typical ration DM
  • Supplies 60-70% of net energy to animals
  • Made up of multiple monosaccharide units linked together
  • 2 major types: structural and non-structural
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3
Q

Structural CHO

A
  • *Support plants as part of cell wall
  • Cellulose
  • Hemicellulose (lignin)
  • Pectin
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4
Q

Lignin

A
  • Phenol groups attached
  • *almost undigestable
    o Don’t want too much in the ration
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5
Q

Non-structural CHO

A
  • Seeds, leaves, stems
  • *energy source for plants
    o Simple sugars or starch
    o Starch=multiple alpha-1,4- glucose linkage (amylose and amylopectin)
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6
Q

Fiber CHO

A
  • Slowly digested structural material
  • Cellulose, hemicellulose, lignin (not pectin)
  • Essential to form rumen mat
  • NDF and ADF
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7
Q

NDF

A
  • Neutral detergent fiber
  • Hemicellulose, cellulose, lignin
  • Digestible portion of fiber
  • *will determine DMI
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8
Q

ADF

A
  • Acid detergent fiber
  • Cellulose, lignin
  • *Least digestible portion (increase ADF=decrease digestibility)
  • Occupies space and limits food intake
  • Too much fiber=decreased feed intake=decreased production
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9
Q

Non-fibre CHO

A
  • Pectins, starch, sugar
  • Take up little space in rumen
  • Completely digested by microbes
    o Also digested by mammalian enzymes
  • *Fermentation much more rapid
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10
Q

CHO digestion/fermentation graph (order)

A
  • Soluble CHO
  • Pectin
  • Cellulose
  • *pH will decrease with non-fiber feed=soluble CHO (ex. grain)
    o Not great for the rumen microflora if large fluctuations
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11
Q

What are some common grains?

A
  • Corn
  • Barley
  • *change from barley to more corn (ex. corn silage)
    o Didn’t have sufficient growing conditions (enough heat), but scientists have developed varieties that will grow
  • **higher in starch and faster digestion
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12
Q

What are the common forages?

A
  • Alfalfa hay
  • Grass hay
  • Corn silage
  • Barley silage
  • Pea silage
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13
Q

Alfalfa hay

A
  • High fiber
  • Moderate non-fiber CHO (NFC)
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14
Q

Grass hay

A
  • Moderate fiber
  • Moderate NFC
  • *will become more fibrous the ‘older’ it gets
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15
Q

Corn silage

A
  • Moderate fiber
  • *moderate-high NFC (higher than barley silage)
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16
Q

Barley silage

A
  • Moderate fibre
  • Moderate NFC
17
Q

Pea silage

A
  • Higher [fat]
  • Lower [protein]
  • *MILK
18
Q

What are the advantages of corn silage?

A
  • Higher NFC due to corn grain
  • **Energy and fiber together!
19
Q

CHO fermentation

A
  • Both structural and non-structural CHO fermented
  • CHO enzymatically degraded to monosaccharides
  • Monosaccharides then broken down to VFA (+ATP)
20
Q

What type of bacteria do we have in the rumen?

A
  • Hydrolytic species: ferment polysaccharides into soluble sugars
  • Hydrolytic + fermentative species: intermediate compounds
  • Fermentative: VFA
  • Methanogen bacteria: produce methane + CO2 (eructed) from H2 + CO2
    o Boluses to reduce methanogen bacteria
21
Q

What are VFA produced and what are they used for? What are some other products produced?

A
  • Acetate=2C
  • Propionate=3C
  • Butyrate=4C
  • **VFA used to make AA or FAs for microbe (transported to liver by PORTAL VEIN)
  • *other products: lactate and other acids (SCFAs)=normally rapidly used up by secondary bacteria
22
Q

Beta-hydroxybutyrate: metabolism

A
  • Used by most tissues for energy
  • Provides initial carbon skeleton for FAs in milk
23
Q

*Propionate (and lactate): metabolism

A
  • Removed by liver
  • **3C
  • Propionate becomes oxaloacetate (4C) then to glucose
  • Lactate to pyruvate, then to glucose
  • *only SCFAs that can form glucose
  • High fiber=less propionate produced
24
Q

*Acetate: metabolism

A
  • Form acetyl-CoA + oxaloacetate = citric acid
  • **used for FA production
  • **More fiber=more acetate produced
25
Q

**High fiber diet: VFA amounts

A
  • Low propionate=less glucose for energy
  • High acetate=more fat in milk production
  • **balancing act
26
Q

What are some of the competing priorities of dairy nutrition?

A
  • Energy requirements for milk production
  • Milk fat
  • Animal health
27
Q

Starch: basic principles

A
  • Digestion can be improved by grinding, rolling, high moisture, steaming, flaking, cooling (increase SA and digestibility)
  • Small amounts could pass SI for digestion
  • Whole grain fed to mature animals can slip out of the rumen undigested=noticeable during preg checks (see in feces)
  • Processing can be beneficial
  • Sheep and goats can chew whole grains, cattle don’t
28
Q

Forage: basic principles

A
  • Fibre length critical
    o Long stem fiber critical for rumen fiber mat
    o BUT ration sorting can occur (dairy cows)
  • If long stem fiber
    o SLOWER passage through rumen
    o Lower feed intake
29
Q

CHO engorgement: rapid intake of gain

A
  • Grain processing increases SA for bacterial fermentation=more rapid VFA and lactic acid produced
  • *amylolytic bacteria (Streptococcus bovis) ferment grain fastest
    o Lactic acid=byproduct
    o D-lactate accumulates in rumen (not used as rapidly as L-lactate)
    o Lower pK=stronger acid than VFAs
  • Lack of fiber=decreased chewing, regurgitation, saliva and less buffers
  • Rumen pH drops
  • *Lactobacilli thrive and produce more lactic acid
  • *protozoa die=starch granules released
30
Q

Ketosis

A
  • FFAs mobilized (due to low glucose from low propionate)
    o Transport to liver
    o Acetyl-CoA normally oxidized via TCA cycle
    o Rate limiting step=oxaloacetate (from propionate)
    o *incomplete oxidation to ketone bodies
31
Q

What are ketones? What are some examples?

A
  • *can be used as energy source and suppress appetite (than getting even less glucose and it perpetuates)
  • Beta-hydroxybutyrate: most common in CATTLE
  • Acetoacetate
32
Q

What might ketosis present as?

A
  • Wasting ketosis
  • Nervous ketosis
  • Pregnancy toxemia (small ruminants)
33
Q

Wasting ketosis

A
  • Clinical or subclinical
  • Decrease in appetite=body weight loss=decreased milk production
  • Ketones on breath (ex. nail polish remover)
34
Q

Nervous ketosis

A
  • Acetoacetate to the brain and forms isopropanol
  • Alcohol in brain and hypoglycemia
    o *circling, straddling/crossing legs, head pressing, delirium
35
Q

Pregnancy toxemia (small ruminants)

A
  • Late pregnancy
  • Very similar to nervous ketosis
36
Q

Impaction

A
  • Off-feed, poor-quality roughage
  • Prolonged feed breakdown
  • Rumen impacted
  • Poorly digested feed escapes to abomasum
  • *abomasal impaction

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