Genetic Diversity in Dutch Sheep Breeds

The Netherlands has a rich variety of native sheep breeds, most of them at risk or endangered. We studied the distinctiveness of these breeds, their genetic diversity within and between breeds, and how this diversity is shaped by geography, purpose, history and genetic management practices. Semen samples of 171 rams of 11 native Dutch breeds were genotyped with the IMAGE001 multispecies SNP chip including 10 K sheep SNPs. Genetic characterisation showed a clear genetic differentiation, except for the Texel and two Texel-derived (sub)breeds. F_ST values were on average 0.124. The largest split was between breeds bred for milk or meat production on rich grasslands in the northwest of the Netherlands and breeds bred for grazing nature areas on poorer grounds in the east. The graphical distribution of the Principal Component Analysis mirrored the geographical distribution of the origin of the breeds. Within-breed diversity was largest for the two breeds with largest population sizes (Texel and Kempen heath sheep) plus the one breed, Veluwe heath sheep, that consistently has used a breeding circle to maintain genetic diversity. The Flevolander, a more recently developed breed based on two foreign breeds, had the highest unique diversity of all breeds. The Texel received the highest ranking after the Flevolander when optimising contributions for the gene bank. As sudden changes in genetic diversity can occur also in large commercial breeds, we recommend that besides safeguarding the endangered breeds, cross sections of the Texel are also stored in the Dutch gene bank.