The Facts about Early Onset Muscle Weakness Syndrome (MW) – Formerly Calf Recumbency  

May 11

What is Early Onset Muscle Weakness Syndrome / Calf Recumbency? 

Early Onset Muscle Weakness Syndrome is a newly discovered genetic condition in Holsteins that can result in affected calves being unable to stand. 

What do we know? 

This unfavorable genetic condition was discovered based on research done at Penn State University, in collaboration with other researchers. This collaboration, which included ABS Global, used sequence data to discover the likely causative mutation in the CACNA1S gene on chromosome 16 (Dechow et al., 2022). It appears to be a recent mutation within a very common Holstein haplotype. More will be learned about the frequency and impact as the industry gathers more information. For more information, please read a joint statement from CDCB, Holstein Association USA, and NAAB

What do we know about carrier animals? 

A gene test was developed to definitively determine animals that are carriers. ABS has test results for most of our marketed bulls, with more test results expected in the upcoming days. All early indications are that ABS has fewer carrier animals in our population than other segments of the industry. The industry is also working to develop a haplotype test, but that is currently unavailable. 

What are the next steps? 

A system is being developed to get test results from laboratories to Holstein USA and CDCB/AGIL. 

Once the industry provides a naming structure, ABS will adopt those labels. In the meantime, we have labeled ABS bulls in the results file as “Carriers” (those that are carriers) and “Free” (those that do not carry the condition). 

ABS Global is committed to ensuring we provide the highest quality genetics and will continue to work with experts across the industry as we all learn more about Early Onset Muscle Weakness Syndrome. ABS will work to incorporate the results into our Bull Search and GMS systems. We will keep you posted as we learn more.