In her doctoral research, Oda Braar Wæge demonstrates how genomic tools can be used to achieve genetic progress while limiting the loss of genetic diversity.
Genomic selection has given livestock breeding a major boost and has led to rapid genetic progress. However, the method also increases inbreeding, which reduces genetic variation and the robustness of animals. In her PhD work, Wæge investigated how genetic diversity can be better managed using genomic data.
Increased inbreeding can lead to inbreeding depression, which often manifests as reduced fertility, poorer health, and weaker production. For breeding programs, this means that short-term progress may conflict with long-term sustainability. A main objective of the dissertation has therefore been to identify strategies that balance these considerations.
Measuring and Controlling Inbreeding
Wæge based her work on Optimal Contribution Selection (OCS), a method used to control how much each breeding animal contributes genetically to the next generation. By combining OCS with genomic information, both genetic progress and inbreeding can be controlled simultaneously.
A central topic is runs of homozygosity (ROH), which are long DNA segments where the alleles are identical on both chromosomes. Such segments can provide information about inbreeding, both recent and more distant. Simulation studies showed that long ROH more often result from inheritance from common ancestors, but also that the detection of ROH is sensitive to how the analyses are set up.
To improve the interpretation of ROH, Wæge and her co-authors therefore developed a new metric that makes it easier to distinguish true inbreeding from random genetic patterns.
Comparison of Genomic Methods
She further compared different genomic measures of relatedness used in OCS. The results showed clear differences between methods. Some provided more precise estimates of genetic relatedness and were better able to preserve genetic variation, while still achieving high genetic progress.
A method widely used in practical breeding also resulted in good progress, but led to gradual changes in allele frequencies that may be unfavorable in the long term.
The choice of method therefore has a major impact on how the population develops genetically.
Tested in Norwegian Cattle
To investigate whether the findings also apply in practice, the doctoral candidate analyzed data from Norwegian Red cattle. The analyses showed a clear relationship between ROH and inbreeding depression, particularly for traits related to production. At the same time, the results showed that different genomic measures can capture different forms of inbreeding.
This suggests that the methods can complement each other and provide a more comprehensive picture of the genetic situation in the population.
Tailored Solutions for Sustainable Breeding
In the dissertation, Wæge concludes that precise genomic methods are best suited for long-term sustainable breeding when high-quality data are available. However, more established methods remain useful in many breeding programs. ROH-based analyses have limitations, but provide valuable insight into historical inbreeding, especially where the data basis is more limited.
According to Wæge, the most important factor is adapting the strategy to both data availability and breeding goals.
Wæge’s work shows that modern genomic tools can be used more strategically to ensure both genetic progress and long-term genetic sustainability in livestock breeding.
Oda Braar Wæge will defend her dissertation “Genomic Strategies for the Management of Genetic Diversity” at the Norwegian University of Life Sciences (NMBU) on 13 May 2026. Professor Theodorus Meuwissen (NMBU) has been Wæge’s main supervisor, and Professor Peer Berg (NMBU) has been her co-supervisor.