Navigating Genomic Testing for Dexter Cattle: Realities and Recommendations

Genomic testing is transforming the beef cattle breeding industry. Breeders of major beef breeds are increasingly using genomic testing to predict traits such as growth potential, carcass quality, and reproductive efficiency. Products like Igenity Beef Profiles have become commonplace in some cattle breeding circles, offering breeding insights—at least for breeds included in the genomic reference populations.

But what about Dexters?

Unfortunately, research consistently underscores a crucial limitation: these genomic tests lose accuracy significantly when applied to breeds not included in their reference datasets. For Dexter cattle, this limitation is especially pronounced. The Dexter breed has yet to be included in any commercial genomic testing panels. As a result, the markers used in current tests do not adequately reflect the unique genetic architecture and variations that influence our breed's traits.

A seminal study by Kachman et al. (2013) found that genomic predictions developed from one breed typically have poor predictive power when applied to another breed not included in the original training set. Similarly, Boerner et al. (2014) confirmed poor prediction accuracy for breeds absent from genomic reference panels. These results have been reinforced by more recent research, consistently highlighting how genomic predictions struggle to accurately capture breed-specific traits without breed-specific data. Dr. Matt Spangler, UNL Beef Genetics Specialist and co-author of the Kachman (2013) paper responded in an open forum to questions related to the use of genetic panels on breeds not in the test panel: "I would not recommend doing so. They can easily lead you astray."

Kachman et al. (2013)

Kachman et al. (2013)

What Does This Mean for Dexter Breeders?

As Dexter breeders, we must face a few realistic implications:

• Inclusion in Existing Genomic Panels is Unlikely: Our breed's limited numbers and distinctive genetics make incorporation into genomic test panels designed for more populous breeds challenging. Major genomic companies have minimal economic incentive to include breeds like ours, and accuracy would remain questionable even if included.

• A Breed-Specific Genomic Test: Ideal but Costly: Dexters would benefit from a breed-specific genomic profile tailored to our breed's unique genetics. However, developing a Dexter-specific genomic test requires substantial investment in genomic sequencing and extensive phenotype collection and analysis. For a small in number breed, like Dexters, the cost is prohibitive.

A More Practical Way Forward

With these challenges in mind, what is the best way for Dexter breeders? A pragmatic alternative focuses on robust phenotypic, genetic, and production-based evaluations. Dexter breeders can make immediate and significant improvements through these methods.

• Breed-Specific Data Collection: By developing and investing effort and resources in the meticulous recording of performance traits, including growth rates, fertility metrics, milk production, and beef production and quality attributes, breeders can strengthen the foundation of Dexter-specific knowledge.

  

• Targeted Genotyping Efforts: While broad genomic predictions might lack validity for Dexters, targeted genotyping—such as parentage verification, genetic diversity assessments, and monitoring known genetic conditions—remains highly valuable.

Performance-Based Evaluations: Through rigorous production data collection and evaluation of beef and dairy production, Dexter breeders can and will enhance the breed's small-scale production market viability, assist in improved selection decisions, and ultimately breed and herd improvement and profitability.

Looking Ahead: Realistic Goals, Real Results

Silver Maple Dexters, for 25 years, has focused on breeding for dual-purpose use and doing so through practical approaches focused explicitly on our breed's realities and strengths. Genomic testing holds exciting possibilities, but Dexter breeders must approach it knowing the significant limitations of current testing options. Tossing dollars at beef panel profile tests that the research clearly indicates are inaccurate and unproductive for our breed is a waste and counterproductive.

Using those same resources and efforts to prioritize careful phenotype recording, breed-specific data collection, and proven production evaluation methods will undoubtedly serve us better in the short and long term. We encourage Dexter breeders to remain engaged and informed in all aspects of the industry and proactively improve our breed into the future. But do so with full knowledge and clear understanding.   

Silver Maple Dexters will soon launch our SMD The Next 25 initiative to move SMD forward into our next phase with Dexter cattle. SMD The Next 25 will provide practical, research-based, and valuable tools and assistance to constructive breeding focused members of the Dexter cattle community. Stay connected for updates on SMD The Next 25 and ongoing discussions and best practices aimed at helping you achieve excellence in your Dexter breeding programs.

Bibliography

Boerner, V., Johnston, D. J., & Tier, B. (2014). Accuracies of genomically estimated breeding values from pure-breed and across-breed predictions in beef cattle. Genetics Selection Evolution, 46(1), Article 61. https://doi.org/10.1186/s12711-014-0061-9

Kachman, S. D., Spangler, M. L., Bennett, G. L., Hanford, K. J., Kuehn, L. A., Snelling, W. M., … & Pollak, E. J. (2013). Comparison of molecular breeding values based on within- and across-breed training in beef cattle. Genetics Selection Evolution, 45(1), Article 30. https://doi.org/10.1186/1297-9686-45-30

Karaman, E., Su, G., Croue, I., & Lund, M. S. (2021). Genomic prediction using multi-breed and admixed reference populations in cattle. Genetics Selection Evolution, 53(1), Article 46. https://doi.org/10.1186/s12711-021-00637-y

Zhao, H., Qin, L., Xu, S., Huang, X., & Liu, G. E. (2024). Integration of multi-omics data to improve genomic prediction accuracy in beef cattle breeding. Biology Direct, 19(1), Article 5. https://doi.org/10.1186/s13062-024-00574-y

Ogawa, S., Matsuda, H., & Okutani, T. (2021). Influence of reference population size on the accuracy of genomic estimated breeding values in Japanese Black cattle. BMC Genomics, 22(1), Article 645. https://doi.org/10.1186/s12864-021-08121-z