Ruminant

Source of CHO: Primarily starch and cellulose

Anaerobic fermentation in rumen!

Starch & cellulose ® glucose ® VFA (propionate, butyrate, acetate), CH₄, CO₂

Type of Diet:

High cellulose = increase rumen acetate = milkfat

High starch = increase rumen proionate = gluconeogenic

Anaerobic Rumen:

No O₂

No electron acceptor

No electron transport

Goal is to regenerate NAD (drives glycolysis and krebs), but in Rumen??

NAD's transfer to pyruvate to form lactate

2 ATP's produced in rumen glycolysis, instead of 6 in cells

CO₂ serves as terminal electron acceptor CO₂ ® CH₄,

Glucose

® lactate ® propionate

® butyrate

® acetate

Lactate build-up in the rumen:

Lactic acidosis

Acidosis

Grain overload

Laminitis

founder

Cause= abrupt increase in starch intake, increases lactate procuction, decreases rumen pH (6.8 ® 5.0).

Occurs when taken from pasture (roughage) and immediately placed on high CHO (corn) diet.

Question?? Acidosis?? Rumen Sample of:

Propionate =	20%
Butyrate =	10%
Acetate =	70%

Not acidosis, propionate from lactate, increase acetate = high forage diet, not a lot of starch

Look at Pro:Ace ratio WHY?

1. Acetic acid ® lost as CH₄ = wastefull

2. Propionate ® less CH₄ more DE trapped as ME!

Factors that Alter Rumen Fermentation

1. Type of CHO = starch increases propionate, cellulose increases acetate.

2. Feed additives = ionophores, alter Pro:Ace, better utilization of feed. A type of antibiotic = selectively inhibits acetate producing microbes.

monensin = Rumensin

lasalocid = Bovatec

3. Total VFA Produced

a. physical form = ground VS. cracked corn = surface area

b. type of CHO = cellulose VS. starch

VFA Metabolism

Acetate ® Acetyl CoA = no gluconeogenesis

Butyrate ® 2 Acetyl CoA = no gluconeogenesis

Propionate ® succinyl CoA = gluconeogenesis

VFA's for energy: Acetate, Propionate, Butyrate

VFA's for Fatty Acid synthesis (Ketogenic): Acetate, Butyrate

VFA's for glucose synthesis (Gluconeogenic): Propionate

Blood Glucose Concentration

Monogastric ~90 - 100 mg.dL

Ruminant ~40 - 60 mg/dL

Difference is because little free glucose absorbed in G.I. tract of ruminant, process of synthesizing glucose = gluconeogenesis.

Gluconeogenesis = glucose synthesis from non-CHO sources

Propionate

Lactate

Glycerol

Some A.A.

3 Irreversable Reactions of Glycolysis: (otherwise = glycolysis backwards)

1. PEP ® pyruvate Þ pyruvate ® oxaloacetate ® PEP

2. Fructose-6-phosphate ® Fructose-1,6-bisphosphate Þ use different enzyme

3. Glucose ® Glucose-6-phosphate Þ use different enzyme