As the dairy industry continues to embrace the power of genomics, we are gaining a much deeper understanding of inherited conditions that affect youngstock vitality. One such development is the identification of Early Onset Muscle Weakness, a genetic disorder impacting some Holstein calves, and we are proud to be part of the solution.

Ground-breaking research into Early Onset Muscle Weakness (MW), led by our parent company STgenetics® in collaboration with respected academic and industry partners, demonstrates the value of genomic science, proactive testing and full transparency.

What is Early Onset Muscle Weakness?

Early Onset Muscle Weakness is a recessive condition that can prevent otherwise healthy Holstein calves from standing at or shortly after birth. While affected calves often show no external deformities, they are unable to rise and may die if not assisted.

After detailed genomic analysis, researchers identified a harmful mutation in the CACNA1S gene on chromosome 16. This mutation affects calcium movement in muscle cells, leading to the weakness observed in afflicted calves.

Advancing Understanding Through Research

The identification of this mutation was made possible by a global research collaboration involving Penn State University, USDA-AGIL and commercial partners. Our parent company, STgenetics®, played a key role in driving this discovery forward, not only helping pinpoint the exact genetic cause, but also validating a direct test to detect carriers of the condition.

Thanks to this work, we can now offer accurate screening for Early Onset Muscle Weakness and make this information fully available and easily accessible to dairy producers, so they can make more informed breeding decisions.

Our Approach: Transparent, Practical, Proactive

At Cogent, we believe in informed choice. We publish full genomic information on all our sires, and we actively test for known recessives, including Early Onset Muscle Weakness. We are committed to equipping our customers with the tools and information they need to protect calf health and manage genetics effectively.

• All Cogent Holstein sires are tested for the CACNA1S mutation
• Results are shared openly via our digital platforms and catalogues
• Genomic testing is available through ST-affiliated labs
• We are committed to have 0% MW carriers in our line-up
• We support responsible breeding by helping customers avoid carrier-to-carrier matings
• We promote genetic diversity to strengthen herd resilience for the long term

We see this as part of a wider commitment to transparency and support. Genetic insights are only useful if they are shared and applied in a way that benefits real-world decision making on farm.

Industry-Wide Context

Recent analysis of the top 200 PLI bulls has revealed that:

• 29 bulls carry a negative haplotype linked to health concerns
• 10 of which are carriers of the Early Onset Muscle Weakness mutation

While these figures may seem small, they highlight the importance of genetic transparency and routine testing across the industry.

To support responsible breeding decisions, we reviewed publicly available data and found a notable spread of carrier bulls across different breeding programmes. The breakdown, shown below, is anonymised but gives an insight into how widespread carrier status can be:

These figures show that Cogent is the only stud with zero carriers of either the CACNA1S mutation or a known negative haplotype among bulls in the top 200 for PLI. This outcome is not coincidental. It reflects our deliberate policy of testing all sires before releasing and maintaining a 0% tolerance for MW carriers in our Holstein line-up.

By combining rigorous genetic screening with transparent sire information, we help farmers make confident, informed breeding decisions that support calf health and long-term resilience.

Looking Ahead

Science is our strongest defence against emerging genetic risks. Early Onset Muscle Weakness is a clear example of how collaboration, transparency and targeted research can lead to healthier herds and more confident breeding decisions.

With technology evolving rapidly, we are likely to uncover more about the genetics behind health, efficiency and performance in dairy herds. By investing in research and sharing results openly, Cogent and STgenetics® aim to lead the way in converting genomic science into practical progress.

We believe that strong herds start with sound genetics, and we are here to help you build them.

To learn more about our testing and our sire portfolio, contact your local Genetics Consultant or call free on 0800 783 7258.