The North American dairy industry is providing early stage advice to protect herds from a recently discovered and potentially fatal genetic defect affecting Holstein calves.
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The first official word on the defect, currently referred to as calf recumbency, came via a joint April 3 press release from the US-based Council on Dairy Cattle Breeding (CDCB), the Holstein Association USA and the National Association of Animal Breeders. .
He said the affected calves are otherwise healthy but unable to stand and, as a result, either die or have to be euthanized.
Because matter: Genetics industry leaders in the United States and Canada are urging Holstein farmers to notify them if a calf cannot stand after birth so tests can be performed for the newly discovered defect.
The inability of newborns to stand has long been associated with inadequate maternal nutrition or trauma during delivery. But recent research from Penn State University and the U.S. Department of Agriculture has confirmed that a genetic defect can also cause the condition.
Considering the animal welfare aspect of this defect, the development of a reliable diagnostic tool is of great importance to consumers, dairy farmers and the dairy genetics industry, the joint US news release said.
The industry recognizes that this flaw needs to be fixed quickly. The priority is to provide access to accurate diagnostic tools with transparent and broad communication of the carrier status of affected males and females.
In early April, two US labs had genetic tests to determine carrier status, and others followed suit in the following weeks. In early May, companies serving Canadian Holstein breeders based in both the US and Canada announced the availability of bearer status information for their sire lineups.
A May 4 announcement from Select Sires’ Ohio headquarters said that the bearer status of its sires was available on its website.
As more AI organizations test and report the bearer status of their bulls, these results will also be added to the database.
Holstein breeders should consider testing their most valuable bitches for this condition, says Select Sires’ announcement. If females are not tested, making strategic decisions about all matings based on known bulls’ pedigrees will provide another layer of protection.
Brian Van Doormaal, chief services officer at Lactanet, said genetic testing offered by some private labs in the US will soon be part of all genotyping services provided through Holstein Canada, Semex and other companies offering genomic testing to farmers canadians. At present, there is no need for farmers to work directly with testing labs (which currently have the test).
We are not yet able to quantify the frequency of this undesirable gene in the Canadian Holstein population. To do that, we need the results of many animals tested for it, and any such tests are just getting started, he said, noting that there’s no reason to expect any significant difference in the prevalence rate, higher or lower. in Canadian Holsteins compared to the US Holstein population.
Van Doormaal notes that Lactanet works closely with the CDCB in the US and all haplotype information and knowledge will be shared openly. He said the CDCB is also working on developing a haplotype analysis procedure to provide reliable results without doing the actual genetic test.
Once developed, CDCB will openly share haplotype results for all animals genotyped with Lactanet.
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This stage would essentially allow all animals to have a carrier probability value displayed for Calf Recumbency on the Lactanet website, he said. I expect this is most likely still a few months away.
Researchers hope to determine an original defect carrier, but the oldest known suspected carrier is Bar-Lee’s US-owned bull Southwind Bell. It is likely that Southwind inherited the region of DNA now known to be affected by the decubitus defect from Osborndale Ivanhoe, one of the founding fathers of the North American Holstein gene pool.
But it’s highly unlikely that Ivanhoe carried the mutation.
It is through Southwinds’ most notable descendants, the Robust and Supersire, that the gene has spread throughout the breed, Semex said in its press release.
The announcement speaks to the complexity researchers are dealing with when it comes to this flaw. The mutation has only recently emerged, so a significant proportion of animals homozygous for that particular region of DNA show no symptoms.
In addition, a producer’s ability to detect a calf with recumbency is difficult when other conditions can also cause it.
Identifying a genetic defect with enough certainty for publication is a lengthy process, noted the joint US news release. This is especially true when phenotypes (observations) are subjective or when calves are euthanized before accurate phenotyping takes place.
The Penn State and USDA research compared the genotypes of 18 postnatal calves that were unable to stand with 26 unaffected calves from the same family groups. All affected calves were homozygous or carried two copies of the affected region of DNA on chromosome 16. This is now referred to as the haplotype of the defect.
The research teams then traced the genotypes of the affected calves’ family trees and determined that the identified haplotype is common and goes back many generations.
The high proportion of symptom-free carriers occur with new mutations because there has not been enough time and data to differentiate the mutated haplotype from the original, normal one, the US news release explains.
Increased validation among available genetic testing data with haplotype data is needed to remove uncertainty and increase reliability so that haplotype testing can be routinely applied to all genotyped animals.
We thank all breeders who have submitted observations and samples to researchers or industry organizations and encourage others to do so in the future. Individual reporting of abnormal calves by farmers remains essential.
US breeding organizations have praised AI companies for working quickly to determine and publish the free or carrier status of their sires. But they also advise Holstein breeders using those bulls that, at this early stage, due to chance in the households sampled, some holdings will have more carrier animals in their populations of donor bulls and cows than others.
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