Bullseye September 2015

HCD: Haplotype Associated with Cholesterol Deficiency

Below is a summary of a CDN Extension Article “Discovering Genetic Anomalies from Genotyping” by Brian VanDoormaal & Lynsay Beavers. For the full article, please visit https://www.cdn.ca/articles.php.

In addition to genomic evaluations and integrity of pedigrees, accumulating thousands of genotypes for a given breed results in the discovery of new genetic anomalies. Scientists in Germany recently discovered a new “Haplotype associated with Cholesterol Deficiency” (i.e.: HCD) in Holsteins, which traces back to Maughlin Storm as the oldest genotyped sire of origin. For calves that inherited the undesirable gene from both parents, it was found that they had an increased incidence of chronic/prolonged diarrhea that was untreatable, as well as other illnesses. Examination of blood samples from affected calves showed a cholesterol deficiency that prevented the normal deposition of fat in body tissues. Over the course of months after birth, the affected calves lost all body reserves and it appears that all eventually died. Without the presence of an exact gene test to identify carriers, the current haplotype analysis can result in some animals being falsely labelled as a carrier if they have both Storm and Willowholme Mark Anthony in their pedigree.

The methodology used by CDN to calculate the HCD Carrier Probability values (varying from 99% for “Carrier” to 1% for “Free”), reduces this problem by combining the haplotype test with pedigree analysis. Now that this undesirable anomaly is known, an industry effort can easily be made to reduce the frequency that carrier animals are mated together, thereby lowering the frequency that homozygous calves are born and subsequently die within months. The discovery of this genetic condition also demonstrates the value and importance of producers reporting to DHI the date and reason for every animal leaving the herd, including young calves.