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Rumen CHO Metabolism. AnSci 520 Lance Baumgard 3-2-10. Feed Efficiencies/ Feed to Gain. Fish (1.2) Broilers (1.9) Turkey (2.6) Swine (2.7) Beef (> 6.0) Why?. CARBOHYDRATES: CHO. CHO function: ENERGY  CHO’s are not an essential nutrient CHO are made of the elements: C arbon

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rumen cho metabolism

Rumen CHO Metabolism

AnSci 520

Lance Baumgard

3-2-10

feed efficiencies feed to gain
Feed Efficiencies/Feed to Gain
  • Fish (1.2)
  • Broilers (1.9)
  • Turkey (2.6)
  • Swine (2.7)
  • Beef (> 6.0)
  • Why?
carbohydrates cho
CARBOHYDRATES: CHO
  • CHO function: ENERGY 
    • CHO’s are not an essential nutrient
  • CHO are made of the elements:
    • Carbon
    • Hydrogen
    • Oxygen
      • Hence the acronym (CHO)
rumen cho metabolism4
Rumen CHO Metabolism
  • Advantage: Can consume worlds most abundant organic compound (cellulose)
    • Increase digestibility
    • Microbes make all of their own amino acids and vitamins
  • Disadvantage:
    • Lose energy as heat and CH4
    • Loss of dietary glucose
rumen cho metabolism5
Rumen CHO metabolism
  • Conversion of dietary macromolecules into pyruvate
  • Starch, cellulose, pectins, and hemicellulose are oxidized to pyruvate
    • 1) Bacterial enzymes hydrolyze plant polysaccharides into monosaccharides
    • 2) Monosaccharides are oxidized by glycolysis into pyruvate
    • 3) Pyruvate is converted into VFA’s, CO2 and CH4
rumen digestion and fermentation
Rumen Digestion and Fermentation

Waste Products

CO2

VFA

Degradable Rumen Microbial cells

CHO microbes NH3

CH4

Heat

Long-chain

fatty acids

H2S

slide7

Microbial Metabolism

Feed

ADP

ATP

NADP+

NADPH

Biosynthesis

Catabolism

VFA

CO2

CH4

Heat

Bacterial Growth

Maintenance

Transport

slide8

Fates of Fermentation Products

Fermentation Products

Organic acids

Microbial protein

Gas (CO2 & Methane)

Rumen

Hindgut

Absorbed

Absorbed

Recycled Absorbed

Feces

Feces

Belch/Bloat

Mary Beth Hall

microbial locations
Microbial locations
  • Adhere tightly to rumen wall
  • Associated with feed particles
  • Float freely in ruminal liquid
  • Microbial Metabolism
    • The lack of O2 limits metabolic options
    • Presented with surplus reducing equivalents (NADH)
      • Therefore they reduce all available compounds
        • CO2 is reduced to CH4
        • Pyruvate is reduced to propionate
        • Acetate is reduced to butyrate
        • Unsaturated fatty acids are reduced to saturated fatty acids
energetic efficiency of vfa fermentation and metabolism
Energetic Efficiency of VFAFermentation and Metabolism

Cellulose

10 Glucose VFA ATP

(6730 kcal) 5240 kcal (1946 kcal)

60A 28.9%

Starch 30P

10B

Absorbed as glucose ATP

(6730 kcal) (2888 kcal)

42.9%

anaerobic vs aerobic metabolism
Glucose

2-5 ATP

Acetate

Propionate

Butryate

Lactate

CO2 and CH4

H2O

Heat

Glucose + O2

36-38 ATP

CO2

H20

Anaerobic vs. Aerobic Metabolism

Doesn’t seem like anaerobic is energetically logical??

slide12

Dietary Polysaccharides

Bacterial enzymes

Monosacharides (glucose: 6 Carbons)

CH4

Glycolysis

H

CO2

Pyruvate (3 C)

Propionate (3C)

Acetate (2 C)

Butryate (4C)

fermentation of glucose and other sugars
Fermentation of Glucose and Other Sugars

Glucose

Pyruvate CO2

Formate Lactate Oxaloacetate

2H

Acetyl-CoA Malate

Acrylate Fumarate

Acetoacetyl CoA

Succinate

MethaneAcetateButyratePropionate Succinyl CoA

Propionyl CoA Methylmalonyl CoA

slide15
Acetate production
    • Pyruvate oxidoreductase (Most common)

Fd FDH2

Pyruvate Acetyl CoA Acetate

Coenzyme A CO2 ADP ATP

    • Pyruvate-formate lyase

Coenzyme A ADP ATP

Pyruvate Acetyl CoA Acetate

Formate

CH4 + H2O

6H+

slide16
Butyrate (60% Butyrate from acetate)
    • Condensation

ATP ADP Acetyl CoA CoA

Pyruvate Acetyl CoA Acetoacetyl CoA

ATP CO2 NADH2

CoA ADP CoA NAD

Malonyl CoA B-Hydroxybutyryl CoA

Crotonyl CoA

NADH2

NAD

Butyryl CoA

Acetyl CoA

Acetate

Butyryl P

ADP

ATP

Butyrate

slide17
Propionate
    • Succinate or dicarboxylic acid pathway
      • 60-90% of propionic acid production

CO2 ATP ADP NADH2 NAD

Pyruvate Oxaloacetate Malate

H2O

CO2 Fumarate

Propionyl CoA ADP NADH2

ATP NAD

Succinate

Propionate

Methylmalonyl CoA Succinyl CoA

slide18
Acrylate pathways
    • Important on high grain diets
      • Accounts of 40% of propionate production
    • NADH2 NAD

Pyruvate Lactate Acrylyl CoA

NADH2

Propionate

NAD

Propionyl CoA

methane
Methane
  • CO2 + 4 H2 CH4 + 2H2O
    • The above is the overall reaction.
    • There are a number of enzymes and cofactors involved
    • in combining CO2 and H2 to form CH4
  • Formate + 3 H2 CH4 + 2H2O
  • CO2 + 2 H 3H2
  • Methane is the predominant hydrogen sink in the rumen
    • Methanogens use H2 as a source of energy

Lyase Preferred pathway

volatile fatty acids
Volatile Fatty Acids
  • Acetate (2 carbons)
  • Propionate (3 carbons)
  • Butryate (4 carbons)
  • All are waste products of microbial metabolism
  • But all are utilized by ruminant animal
energy supply to ruminants
Energy Supply to Ruminants

VFA 70%

Microbial cells 10%

Digestible unfermented feed 20%

Concentration of VFA in the rumen =

50 to 125 uM/ml

utilization of fermentation nutrients
Utilization of fermentation nutrients
  • 70-80% of dietary calories and 2/3 of total digestible dry matter are absorbed across rumen wall
  • Rate of diffusion into rumen epithelial cells varies with rumen pH and VFA chain length
    • pH = absorption
    • Butyrate > propionate > acetate
absorption of vfa
Absorption of VFA
  • 70% of VFA absorbed from rumen-reticulum
  • 60 to 70% of remainder absorbed from omasum
    • Papillae are important – provide surface area
  • Absorption from rumen is by passive diffusion
    • Concentration in portal vein less than rumen
        • VFA concentrations
          • Rumen 50 - 150 mM
          • Portal blood 1 - 2 mM
          • Peripheral blood 0.5 - 1 mM
  • Absorption increases at lower pH
        • H+ + Ac- HAc (free form of the acid)
    • Undissociated acids (free form) diffuse more readily
  • At pH 5.7 to 6.7 both forms are present, however most acids are dissociated: At higher pH, 1 equiv of HCO3 enters the rumen with absorption of 2 equiv of VFA
vfa absorption absorption of ac ates
VFA AbsorptionAbsorption of Ac- (ates)

Rumen

Ac- Ac-Portal

HAc blood

H+Metabolism

HCO3-

H2O H2CO3

+

CO2 CO2 Carbonic

Metabolismanhydrase

HAc HAc

Dissociated:

Free Form:

vfa absorption
VFA Absorption
  • Rate of absorption:
    • Butyrate > Propionate > Acetate
  • Absorption greater with increasing concentrations
  • of acids in the rumen
  • Absorption increases at lower rumen pH
  • Absorption greater in grain fed animals
    • Faster fermentation – More VFA produced
    • Lower pH
    • Growth of papillae
acetate utilization
Acetate Utilization
  • Absorbed through rumen wall
    • Small amt converted to ketone bodies
    • Most carried by portal circulation to liver
      • 20% converted to acetyl-CoA in hepatocyte cytoplasm
      • 80% escape oxidation and is exported from liver
      • Absorbed by extra-hepatic cells and used for
        • Energy via the TCA cycle
        • Fatty acid synthesis
utilization of acetate in metabolism
Utilization of Acetate in Metabolism

1. Acetate (As energy) Energy

Acetate Acetyl CoA Krebs cycle 2 CO2

2 carbons (10 ATP/mole)

2. Acetate (Carbon for synthesis of fatty acids – in AT or MG)

Acetate Acetyl CoA Fatty acids Lipids

H+NADPH NADP+

Glycerol

Pentose PO4 CO2

shunt Glucose

propionate utilization
Propionate Utilization
  • Absorbed through rumen wall
    • 2-5% converted to lactic acid by rumen enterocytes
    • 95-98% travels to liver
      • Converted to succinyl-CoA
        • Then converted to glucose
utilization of propionate in metabolism
Utilization of Propionate in Metabolism

Propionate

Propionate Propionyl CoA Methylmalonyl CoA

CO2 Succinyl CoA

Glucose Krebs

cycle 2 CO2

Energy

(18 ATP/mole)

utilization of butyrate
Utilization of butyrate
  • Absorbed through rumen wall
    • Used by rumen epithelial cells as an energy source
    • Largely converted to ketones
      • 80% converted into -hydroxybutryic acid (HBA)
    • Very low butyrate levels in blood
    • HBA is oxidized in cardiac and skeletal muscle or utilized for fatty acid synthesis in adipose tissue (AT) or mammary gland
utilization of butryate in metabolism
Utilization of Butryate in Metabolism

Butyrate (As energy)

Butyrate Butyrl CoA B-hydroxybutyrate Acetyl CoA

Krebs

cycle 2 CO2

Energy

(27 ATP/mole)

Some butyrate also used as a primer for short-chain fatty acids

slide33

Liver

Glucose is made from propionate

Lactose is made from glucose

Milk yield is determined by the amount of synthesized lactose

Glucose

(from Propionate)

ATP

Propionic

Feed

Acetic

Butyric

Lactose

Bacteria

Milk Fat

Milk Yield

utilization of vfa in metabolism summary
Utilization of VFA in MetabolismSummary

Acetate

Energy

Carbon source for fatty acids

Adipose

Mammary gland

Not used for net synthesis of glucose

Propionate

Energy

Precursor of glucose

Butyrate

Energy

Carbon source for fatty acids - mammary

lower energy value of roughage compared with grain
Lower Energy Value of Roughage Compared with Grain
  • Less digested
    • Lignin limits digestibility of digestible fiber
  • - Greater energy lost from fermentation
    • CH4&Heat
  • - Increased rumination
  • Rumen contractions
  • Chewing
  • - More bulk in digestive tract
comparative prices of corn and alfalfa hay37
Comparative Prices of Corn and Alfalfa Hay

*Market prices as of June 2008

concentrates decrease ph
Concentrates decrease pH
  • Eating and ruminating times are reduced, therefore decreased saliva production
  • Rate and extent of acid production is greater
  • Forages exert some buffering capacity
  • Slower rate of exit
slide39

Dietary effects on

Rumen CHO metabolism

effect of diet on vfa ratios
Effect of Diet on VFA Ratios
  • Forage:Grain -----Molar ratios-----
    • Acetate Propionate Butyrate
    • 100:0 71.4 16.0 7.9
    • 75:25 68.2 18.1 8.0
    • 50:50 65.3 18.4 10.4
    • 40:60 59.8 25.9 10.2
    • 20:80 53.6 30.6 10.7

VanSoest

slide41
VFA production
    • Usually peaks 4 hours after feeding
    • Concentration does not equal production
    • Factors that increase propionate, decrease acetate and methane
    • Factors affecting VFA produced
      • Diet forage:concentrate ratio
        • Decreased forage and increased concentrate
          • Decreased acetate and methane, increased propionate
        • Dietary buffers
          • Increased acetate and methane, decreased propionate
        • Decreased physical form of diet (grinding, pelleting etc)
          • Decreased acetate and methane, increased propionate
        • Ionophores
          • Decreased acetate and methane, increased propionate
        • Unsaturated fatty acids
          • Decreased methane, increased propionate
slide42
Examples of diet effects on VFA production
    • Forage:Concentrate

Forage:Concentrate

VFA, Molar%60:4040:6020:80

Acetate 66.9 62.9 56.7

Propionate 21.1 24.9 30.9

Butyrate 12.0 12.2 12.4

Methane, Mcal/d 3.1 2.6 1.8

    • Physical form of forage

Alfalfa hay

Grind

VFA, Molar%LongCoarseFinePelleted

Acetate 62.5 56.8 47.5 18.2

Propionate 23.8 27.1 28.5 45.7

Butyrate 10.8 13.6 23.9 32.8

slide43

sugars

Starches and pectin

starches

celluloses

G. Varga

starch
Starch
  • Dietary Allowance: 25-35% of DM as starch
    • Varies depending on ruminal starch degradability
  • Ruminal Degradability varies with:
    • Type of grain
      • Barley or wheat > corn
    • Harvest and Storage method
      • High moisture corn > dry corn
      • For high moisture corn, degradability increases with moisture
    • Processing
      • Degradability increases with fineness of grind
      • Starch in steam flake corn is rapidly degraded in the rumen
      • Starch in rolled corn silage degardes faster than if “”unrolled”.

Michel Wattiaux

tissue metabolism vfa
Tissue MetabolismVFA
  • VFA GIT tissues Liver
  • Body tissues
  • Use of VFA
    • Energy
    • Carbon for synthesis
      • Long-chain fatty acids
      • Glucose
      • Amino acids
      • Other
effect of vfa on endocrine system
Effect of VFA on Endocrine System
  • Propionate
    • Increases blood glucose
    • Stimulates release of insulin
  • Butryate
    • Not used for synthesis of glucose
    • Stimulates release of insulin
    • Stimulates release of glucagon
      • Increases blood glucose
  • Acetate
    • Not used for synthesis of glucose
    • Does not stimulate release of insulin
  • Glucose
    • Stimulates release of insulin