Selection for scrapie resistance and simultaneous restriction of inbreeding in the rare sheep breed "Mergellander"

Research output: Contribution to journalArticleAcademicpeer-review

11 Citations (Scopus)


Scrapie is a fatal infectious neurodegenerative disease for which susceptibility is associated with polymorphisms in the ovine prion protein (PrP) gene. Scrapie-eradication programmes are based on eliminating the susceptible VRQ allele and/or breeding for the resistant ARR allele. In rare breeds or breeds with a low frequency of the ARR allele this can lead to unacceptably high inbreeding rates with associated increased risk of genetic defects and inbreeding depression. The conservation status of populations with inbreeding rates (¿F) above 1% is considered critical. In the Dutch rare sheep breed the Mergellander animals carrying ARR alleles are closely related to one another, and could reach 1.53% when only ARR/ARR animals are used as parents. Inbreeding rates can be reduced by selecting the set of parents according to their average co-ancestry. We minimised inbreeding rates by calculating the optimal contribution of each ram and selection of ewes. This resulted in inbreeding rates of ¿0.17% with exclusive use of homozygous ARR rams, and ¿0.38% if use of heterozygous rams was allowed as well. Thus sophisticated breeding programs can prevent unacceptably high inbreeding rates when breeding for scrapie resistance.
Original languageEnglish
Pages (from-to)161-171
JournalPreventive Veterinary Medicine
Issue number2
Publication statusPublished - 2007


  • animal breeding
  • sheep
  • rare breeds
  • sheep breeds
  • ewes
  • rams
  • disease resistance
  • disease control
  • inbreeding
  • inbreeding depression
  • disease prevention
  • breeding programmes
  • scrapie
  • scrapie agent
  • alleles
  • mergelland sheep
  • prp genotype frequencies
  • natural scrapie
  • association
  • gene
  • populations
  • codon-136
  • survival


Dive into the research topics of 'Selection for scrapie resistance and simultaneous restriction of inbreeding in the rare sheep breed "Mergellander"'. Together they form a unique fingerprint.

Cite this