13 – Rumen CHO, Fibre, Fermentation Flashcards
(36 cards)
1
Q
How much glucose does a lactating dairy cow need per day (liver)?
A
- 5kg/day
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
3
Q
Structural CHO
A
- *Support plants as part of cell wall
- Cellulose
- Hemicellulose (lignin)
- Pectin
4
Q
Lignin
A
- Phenol groups attached
- *almost undigestable
o Don’t want too much in the ration
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)
6
Q
Fiber CHO
A
- Slowly digested structural material
- Cellulose, hemicellulose, lignin (not pectin)
- Essential to form rumen mat
- NDF and ADF
7
Q
NDF
A
- Neutral detergent fiber
- Hemicellulose, cellulose, lignin
- Digestible portion of fiber
- *will determine DMI
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
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
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
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
12
Q
What are the common forages?
A
- Alfalfa hay
- Grass hay
- Corn silage
- Barley silage
- Pea silage
13
Q
Alfalfa hay
A
- High fiber
- Moderate non-fiber CHO (NFC)
14
Q
Grass hay
A
- Moderate fiber
- Moderate NFC
- *will become more fibrous the ‘older’ it gets
15
Q
Corn silage
A
- Moderate fiber
- *moderate-high NFC (higher than barley silage)
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
**High fiber diet: VFA amounts
- Low propionate=less glucose for energy
- High acetate=more fat in milk production
- **balancing act
26
What are some of the competing priorities of dairy nutrition?
- Energy requirements for milk production
- Milk fat
- Animal health
27
Starch: basic principles
- 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
Forage: basic principles
- 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
CHO engorgement: rapid intake of gain
- 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
Ketosis
- 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
What are ketones? What are some examples?
- *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
What might ketosis present as?
- Wasting ketosis
- Nervous ketosis
- Pregnancy toxemia (small ruminants)
33
Wasting ketosis
- Clinical or subclinical
- Decrease in appetite=body weight loss=decreased milk production
- Ketones on breath (ex. nail polish remover)
34
Nervous ketosis
- Acetoacetate to the brain and forms isopropanol
- Alcohol in brain and hypoglycemia
o *circling, straddling/crossing legs, head pressing, delirium
35
Pregnancy toxemia (small ruminants)
- Late pregnancy
- Very similar to nervous ketosis
36
Impaction
- Off-feed, poor-quality roughage
- Prolonged feed breakdown
- Rumen impacted
- Poorly digested feed escapes to abomasum
- *abomasal impaction
