1. Managing lethal alleles using genomic optimum contribution selection
Line Hjortø
Jørn Rind Thomasen
Peer Berg
Morten Kargo
Mark Henryon
Huiming Liu
Christian Sørensen

2. Hypotheses
Culling carriers of recessive lethals reduce genetic gain obtained from truncation selection Optimum-Contribution Selection reduces frequency of recessive lethal without compromising genetic gain

3. Design Selection Culling of carriers Truncation OCS with pedigree
OCS with G-matrix
Culling of carriers
None
Male carriers
Female carriers
All carriers

4. Genetic Models Frequency of recessive lethal allele
0.05, 0.10, or 0.15
Effect on Breeding Goal
0 or 3% of VA explained by lethal
Linked to other QTLs
Yes or No

5. at the same rate of true inbreeding, IBD
Criterion
Genetic gain
at the same rate of true inbreeding, IBD
Assessed the two constraints by rate of genetic gain per rate of true inbreeding.
Rate of genetic gain was measured as average true breeding value.
Rate of true inbreeding was measured as proportion of homozygosity at unique

6. Relative initial genetic gain
Truncation
OCS - ped
OCS - gen
No culling
100%
102%
99%
All carriers culled
81%
104%
Male carriers culled
93%
97%
Female carriers culled
88%
98%
Large interaction exist

7. Relative long-term genetic gain
Truncation
OCS - ped
OCS - gen
No culling
100%
112%
All carriers culled
113%
Male carriers culled
Female carriers culled
101%
No interaction

8. At the same rate of true inbreeding
Truncation 61 sires OCS using pedigree 35 sires OCS using genomic information 32 sires OCS selects stronger within families, while truncation selects more males to cover enough families

9. Frequency of lethal allele
OCS - gen
OCS - ped
Truncation
Generation

10. Summary
Carrier culling reduces initial genetic gain of truncation selection Carrier culling of a single lethal does not affect long-term genetic gain OCS tend to slow natural selection against lethal OCS tidy up the mess from carrier culling

11. OCS should be used, when carriers are culled in a pre-selection step
Conclusion
OCS should be used, when carriers are culled in a pre-selection step