Effect of PrP genotype on milk traits in Bovška sheep

Abstract. The aim of this study was to evaluate the effect of PrP genotype on milk traits in the Slovenian autochthonous Bovška sheep breed. The estimated population size is 3 700 animals, half of which are included in the selection programme. Genetic resistance for scrapie, a well known prion disease, is determined by the genotype at the PrP locus. In 2003, the Slovenian National Scrapie Programme following EU Regulations was introduced to control scrapie by selecting out the less resistant genotypes and until 2008, a total of 1 875 ewes were genotyped. This study determined frequencies of PrP alleles in Bovška sheep, AHQ 17.32 %, ARH 7.30 %, ARQ 57.14 %, ARR 17.12 % and VRQ 1.12 %, which were very similar to frequencies in other European breeds. The PrP genotype had a significant effect on milk, protein and lactose yield produced in lactation, but the productivity of the most resistant ARR/ARR homozygotes was similar to breed average and did not statistically differ from other genotypes. Heterozygotes AHQ/ARH, AHQ/ARQ and ARH/ARQ exhibited significantly higher productivity compared to respective homozygotes but not from the most resistant ARR/ARR genotype. It is expected therefore that increased frequency of the ARR allele or even its exclusivity will not directly influence the productivity of the breed. However, a careful management programme favouring resistant PrP genotypes should be implemented to reduce potential negative effects of productivity due to reduced selection potential or inbreeding.