Ruminant VFA digestion

Question 1

What are the 3 styages of microbial CHO metabolism?

Answer 1

1. extracellular hydrolysis
2. intracellular glycolysis
3. VFA production

Question 2

What happens during extracellular hydrolysis?

Answer 2

• microbes produce hydrolase enzymes - break down long chain polysaccharides to mono- and disaccharides
• enzymes - cellulase, pectinase, hemicellulase, a-amylase, sucrase
• products - hemicellulose, pectin, cellulos, starch, sucrose, fructans

Question 3

What happens during intracellular hydrolysis?

Answer 3

• products of stage 1 enter glycolysis where they are metabolised anaerobically
• products - pyruvate, ATP, NADH

Question 4

What happens during VFA production?

Answer 4

Microbes convert pyruvate to VFA through a number of different pathways

Question 5

What is the fate of the VFA?

Answer 5

• absorbed through the rumen wall
• acetate - in tissues is converted to acetyl CoA - used for E/FA synthesis
• propionate - absorbed by liver, substrate for gluconeogenesis
• butyrate - converted to B-OHbutyrate in rumen wall, circulates to tissues where is absorbed and converted to acetyl CoA by ketone body pathway