Holstein calves have recently been discovered to be demonstrating a new genetic defect. The USDA, university researchers, and dairy genetics companies are working together to tackle the defect, currently labeled a “Calf Recumbency.”
Affected newborn calves with the defect are characterized by being weak and unable to stand at birth or shortly after, while otherwise appearing healthy. Research by Dr. Chad Dechow at Penn State University showed that most of the calves his team studied with the defect did not survive beyond 6 weeks of age.
Dechow’s research has compared the genotypes of 18 affected and 26 unaffected calves, and determined the mutation that causes Recumbency is located on chromosome 16. They were able to identify the haplotype or segment of DNA that affects Recumbency, and found that all affected calves were homozygous for the gene, meaning they had inherited two copies of it – one from each parent.
More analysis led to identifying the actual gene that causes Recumbency. Then, through pedigree tracing, a common sire born in 2008 was identified in both the paternal and maternal lineages of all affected calves.
The National Association of Animal Breeders (NAAB) has noted that the defect must be addressed quickly. “The priority is to provide access to accurate diagnostic tools with transparent and wide communication of carrier statuses of affected males and females,” the NAAB stated in a recent news alert.
The USDA’s Animal Improvement and Genomics Laboratory (AGIL) and the Council on Dairy Cattle Breeding (CDCB) currently are working together to develop a haplotype-based test that can be applied to all genotyped animals. This test is not yet commercially available.
In the meantime, there are two tests available to determine carrier status of the defect. Artificial Insemination (AI) companies currently are testing their bulls using either the Genetic Visions-STTM or Feanix Bio test to determine whether or not each sire is positive for the mutation.
STgenetics, owner of the Genetic Visions-STTM test, noted in a recent bulletin on Calf Recumbency that producers who genomically test their females for Recumbency can eradicate the mutation from their herds by only breeding non-carrier females to non-carrier bulls, or using their more advanced Chromosomal Mating® service to avoid mating carrier females to carrier bulls.
Validating the preliminarily identified genetic location of the defect will rely heavily on genetic sampling of affected calves, along with as many of their family members as possible. To do so, it will be important for producers to report the defect in their herds and collect tissue samples in cooperation with their veterinarians.
One of the challenges with this particular defect, however, is that recumbency issues in newborn calves can have multiple origins. While the cause may be the genetic defect, newborn calves also may be unable to stand due to physical trauma from a difficult birth, or nutritional deficiencies.
Producers should be on the lookout for newborn calves that show the symptoms of weakness or paralysis and the inability to stand, either immediately after birth, or within the first 6 weeks of life, and report those animals as they are detected.
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