Haplotype for Cholesterol Deficiency
(North America) HCD, or Haplotype for Cholesterol Deficiency A farm in the northeast had two Holstein embryo transfer calves that presented with chronic diarrhea and progressive emaciation. The herd veterinarian suspected Haplotype for Cholesterol Deficiency (HCD) and submitted serum for chemistry panels on the calves.
Cholesterol and triglyceride results are as follows:
- Cholesterol 14 mg/dL (ref range 163-397)
- Triglycerides < 9 mg/dL (ref range 10-19)
- Cholesterol 138 mg/dL (ref range 163-397)
- Triglycerides 16 mg/dL (ref range 10-19)
These results are highly suspicious of HCD, which 'is most probably codominantly inherited because calves carrying one copy of the haplotype show intermediate cholesterol values.' Calf 1 could be a carrier, while calves 2 is most likely homozygous.
HCD is an inherited homozygous recessive disease in Holstein cattle. It causes hypocholesterolemia resulting in chronic diarrhea, severe weight loss, and eventually death in calves by six months of age. The genetic mutation is a lack of apolipoprotein which causes 'malabsorption of dietary fat and fat-soluble vitamins in the intestine and is assumed to impair cholesterol metabolism and transport in the circulation and the liver.' These calves have marked hypocholesterolemia on serum chemistry panels.
The original bull to carry the genetic mutation is Maughlin Storm, born in 1991. Currently, the registration number of the dam and sire can be entered on the Holstein Association to determine if the offspring is heterozygous or homozygous. Alternatively, genetic testing can be performed at the Veterinary Genetic Lab at UC Davis or Gene Seek at Neogen in Nebraska. The results are read out as normal, carrier (heterozygous) or affected (homozygous). If two carriers are bred, one can expect a 25% chance of a homozygous calf.
Sources: J. J. Gross, et al. 'Rapid Communication: Cholesterol deficiency 'associated APOB mutation impacts lipid metabolism in Holstein calves and breeding bulls' Switzerland 2016.
S. Kipp, et al. 'Identification of a haplotype associated with cholesterol deficiency and increased juvenile mortality in Holstein cattle' J. Dairy Sci. 99 :8915'8931. 2016.