Topics:
Animal Nutrition, Animal Refresher
Absorption Rate of Volatile Fatty Acids
Rate of VFA absorption across the rumen wall follows the order:
- Butyrate > Propionate > Acetate — Correct Answer
- Propionate > Acetate > Butyrate
- Acetate > Propionate > Butyrate
- None
Explanation:
Correct Answer: Butyrate > Propionate > Acetate
The rate of VFA absorption across the rumen wall follows the order: Butyrate > Propionate > Acetate. This is because absorption rate is related to the lipid solubility and chain length of the VFA — longer chain and more lipophilic acids (butyrate) diffuse faster across the epithelial membrane.
VFA Absorption Characteristics
| VFA | Chain Length | Absorption Rate | Rumen Proportion |
|---|---|---|---|
| Butyrate (C4) | 4 carbons | Fastest ✓ | ~10% |
| Propionate (C3) | 3 carbons | Intermediate | ~20% |
| Acetate (C2) | 2 carbons | Slowest | ~65% |
Mechanism of VFA Absorption
- VFAs are absorbed by passive diffusion — no energy expenditure required.
- Undissociated (protonated) form of VFA diffuses more readily → favoured at lower rumen pH.
- The rumen papillae provide the large surface area needed for rapid VFA absorption.
- Butyrate is rapidly converted to β-hydroxybutyrate within the rumen epithelial cells themselves before entering portal blood.
Why Other Options Are Wrong
- Propionate > Acetate > Butyrate → incorrect order; butyrate, not propionate, is fastest.
- Acetate > Propionate > Butyrate → completely reversed; acetate (most abundant but smallest) is absorbed most slowly.
- None → Butyrate > Propionate > Acetate is the established order.
📚 About this Topic — Animal Nutrition
This multiple choice question is from Animal Nutrition, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Nutrition to strengthen your preparation.
