A new genetic defect was recently identified within the Holstein breed. This genetic defect – called calf recumbency – is an important concern and high priority for you as a producer and GENEX, as your genetic supplier. Below, you will find questions and answers explaining the genetic defect and our approach to mitigating its impact. Please note, this genetic defect has proven more complex than other recent genetic defects and additional research and testing is being conducted. For further details, read this industry statement on recumbency in Holstein calves from the Council on Dairy Cattle Breeding (CDCB), National Association of Animal Breeders and Holstein Association-USA.
What is recumbency in Holstein calves?
Calf recumbency is a genetic defect that affects Holstein calves’ ability to stand. Calves affected by recumbency are unable to stand at birth or lose the ability to stand shortly after birth.
What is the frequency of calf recumbency in the Holstein population?
Currently, the population frequency is unclear; however, calf recumbency has been traced back to some influential Holstein bloodlines and is likely to be present in all A.I. breeding programs to some degree.
In particular, influential bloodlines that carry this genetic defect trace back to Roylane Socra Robust and his son Seagull-Bay Supersire (both are carriers of calf recumbency). We can assume there will be more as further testing is conducted.
A gene test has been developed using research by scientists at Penn State University that can identify carrier animals, but a haplotype test is not yet available from CDCB.
How can I mitigate the impact of calf recumbency on my herd?
In the future, GENEX MAP+™ or GENEX DairySuite™ mating programs will have the capability to avoid mating known carriers. This, however, will require programming, a data source and an industry source file (which is not yet available) before this capability can be added to these programs.
Where can I access calf recumbency test results on GENEX bulls?
As of today (April 24, 2023), we have received test results on the majority of our active lineup. Results on the full active lineup will be made available as results are received. To be transparent, we are committed to testing our most recently used bulls from the past five years.
To access a full list of GENEX Holstein sires tested to date, click the button below.
How are the test results labeled?
The tested bulls have been grouped into three categories: Free, Carrier or Affected. The bulls listed as “Free” are tested free for calf recumbency. Those labeled “Carrier” have tested heterozygous for calf recumbency, and those labeled “Affected” are considered homozygous for calf recumbency.
Note that this deviates from the historic understanding of genetics where a homozygous designation (Affected) is traditionally lethal. At this point, it is believed the affected individuals may have recovered from calf recumbency, but the reason is not yet fully understood.
Also note that consistent and concise labeling is being established across the industry to ensure calf recumbency is universally recognized. Once decided and available, we will add and update labeling across our GENEX platforms.
What percentage of animals would result in a lethal outcome if random mating took place?
While we do not know exact details or prevalence in the population, we can provide an example based on a reasonable prevalence rate. If the prevalence rate is 10%, then the risk of a lethal outcome is 0.25% of randomly mated animals (see below).
If you have further questions, regarding the recumbency genetic defect impacting Holstein calves, please reach out to your local GENEX representative.