Topics:
Animal Nutrition, Animal Refresher
Pathways of Urea Recycling in Ruminants
The main path of urea recycling is:
- By way of saliva
- Through ruminal wall/portal blood
- Both a & b — Correct Answer
- None
Explanation:
Correct Answer: Both a & b (via saliva AND through ruminal wall/portal blood)
Ruminants efficiently recycle endogenous urea through two pathways: (1) via saliva — the parotid and other salivary glands secrete significant amounts of urea-containing saliva into the rumen, and (2) through the ruminal wall — blood urea passes across the rumen epithelium (portal blood → rumen) by diffusion.
Urea Recycling Pathways in Ruminants
| Pathway | Mechanism | Proportion of Recycling |
|---|---|---|
| Salivary recycling | Urea secreted in saliva → rumen | ~30–40% of hepatic urea |
| Trans-ruminal wall | Blood urea → rumen epithelium → rumen | ~60–70% of hepatic urea |
Significance of Urea Recycling
- Allows ruminants on low-protein diets to conserve nitrogen — crucial for survival in N-deficient environments.
- Recycled urea is hydrolyzed by rumen bacteria → NH₃ → microbial protein synthesis.
- Total recycled urea can be 40–80% of daily urea production.
Why Other Options Are Wrong
- By way of saliva only → incomplete; trans-ruminal wall passage is equally important.
- Through ruminal wall only → incomplete; salivary recycling is also a major pathway.
- None → both pathways are well-established and scientifically proven.
📚 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.
