Advantages of Open Nucleus System (ONBS)
ONBS is better than CNBS, because in ONBS-
- Bidirectional gene flow takes place
- Nucleus herd is open for introduction of superior animals
- Reduced rate of inbreeding & greater response to selection is observed
- All correct — Correct Answer
Explanation:
Correct Answer: All correct
ONBS is superior to CNBS because of all three advantages listed — all are correct and derived directly from the defining features of an open vs closed system.
ONBS vs CNBS — Full Comparison
| Feature | CNBS | ONBS |
|---|---|---|
| Gene flow | Unidirectional only (N→M→V) | Bidirectional (N↔M↔V) |
| Nucleus herd | Closed — no entry from base population | Open — superior base females can enter nucleus |
| Inbreeding | Higher rate | Reduced rate |
| Genetic progress | Lower | Greater response to selection (10–15% higher) |
| Species used | Pigs & Poultry | Cattle, Buffalo, Sheep |
Special Notes
- ONBS is better than CNBS overall
- Sire selection in both NBS: Sibling test
- For faster genetic improvement: ONBS + MOET
- Sibling test preferred over progeny testing in NBS due to shorter generation interval → higher ΔG/year
📚 About this Topic — Animal Genetics & Breeding
This multiple choice question is from Animal Genetics & Breeding, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Genetics & Breeding to strengthen your preparation.
