Topics:
Animal Nutrition, Animal Refresher
Mechanism of VFA Absorption
The absorption of VFA occurs in ruminant by:
- Active transport
- Passive diffusion — Correct Answer
- Facilitated transport
- None
Explanation:
Correct Answer: Passive diffusion
VFA (Volatile Fatty Acids) are absorbed across the rumen wall by passive diffusion — no energy (ATP) is required. The concentration gradient drives movement of undissociated (protonated) VFA molecules from the high-concentration rumen lumen across the lipid bilayer of rumen epithelial cells into portal blood.
Absorption Mechanisms in the GIT
| Substance | Absorption Mechanism | Site |
|---|---|---|
| VFAs (in ruminants) | Passive diffusion | Rumen wall (papillae) |
| Glucose (in non-ruminants) | Active transport (Na⁺-dependent) | Small intestine |
| Amino acids | Active transport | Ileum (ruminants); Duodenum/jejunum (non-ruminants) |
| Fatty acids (long-chain) | Passive diffusion (as micelles) | Proximal jejunum |
Factors Affecting VFA Absorption Rate
- Rumen pH → lower pH → more undissociated VFA → faster passive diffusion.
- Chain length → Butyrate > Propionate > Acetate (lipid solubility increases with chain length).
- Surface area → rumen papillae size and density determine absorption capacity.
Why Other Options Are Wrong
- Active transport → requires ATP and carrier proteins; VFA absorption across rumen wall does not require energy input.
- Facilitated transport → uses carrier proteins but no ATP; not the established mechanism for ruminal VFA absorption.
- None → passive diffusion is the correct and well-established mechanism.
📚 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.
