Topics:
Animal Nutrition, Animal Refresher
Escape Proportion of Dietary Protein
______% of the dietary true protein escapes ruminal digestion.
- 30
- 40 — Correct Answer
- 50
- 60
Explanation:
Correct Answer: 40%
Approximately 40% of dietary true protein escapes ruminal digestion — this is the UDP (Undegradable Dietary Protein) or RUP (Rumen Undegradable Protein) / Bypass Protein fraction. The remaining ~60% is degraded in the rumen by microbial enzymes to ammonia and amino acids, which are then used for microbial protein synthesis.
Rumen Protein Digestion — Partitioning
| Fraction | Approximate % | Fate |
|---|---|---|
| RDP (Rumen Degradable Protein) | ~60% | Degraded to NH₃ → microbial protein synthesis |
| RUP / UDP / Bypass Protein | ~40% | Escapes rumen → digested in small intestine |
Significance of Bypass Protein
- High-producing dairy cows need bypass protein to meet their post-ruminal amino acid requirements.
- Microbial protein (from RDP) alone is insufficient for peak lactation requirements.
- Examples of high natural bypass proteins: Maize zein, Feather meal, Blood meal (20–40% degradable).
- Examples of low bypass (high RDP): Urea (100%), Casein (90–95%).
Why Other Options Are Wrong
- 30% → underestimates bypass fraction; accepted standard is ~40%.
- 50% → overestimates; 50% RUP would imply equal degradable/undegradable fractions.
- 60% → this is the proportion DEGRADED in rumen (RDP), not the escape fraction.
📚 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.
