Topics:
Animal Physiology, Animal Refresher
Rate of VFA Absorption Order
Rate of VFA absorption is:
- Butyrate < Propionate < Acetate
- Propionate < Acetate < Butyrate
- Acetate < Propionate < Butyrate — Correct Answer
- None of the above
Explanation:
Correct Answer: Acetate < Propionate < Butyrate
The rate of VFA absorption across the rumen wall follows the order: Acetate < Propionate < Butyrate, meaning butyrate is absorbed fastest and acetate slowest.
Reason for This Order
- VFAs are absorbed by passive diffusion in their undissociated (lipid-soluble) form.
- Lipid solubility increases with chain length: Butyrate (C4) > Propionate (C3) > Acetate (C2).
- Higher lipid solubility = faster passive diffusion through the lipid bilayer of rumen epithelium.
Mnemonic
'Bigger chain = Better absorption' — Butyrate has 4 carbons, propionate has 3, acetate has 2; hence butyrate is absorbed fastest.
Quantitative Contribution of VFAs in Rumen
- Acetate: ~60–70% of total VFA (most abundant)
- Propionate: ~15–20%
- Butyrate: ~10–15% (least abundant but absorbed fastest)
VFAs together supply about 70% of the ruminant's total metabolizable energy requirement.
📚 About this Topic — Animal Physiology
This multiple choice question is from Animal Physiology, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Physiology to strengthen your preparation.
