The effect of insertion/deletion polymorphisms within the promoter and intron 1 sequences of the PRNP gene on the breeding value of Holstein-Friesian bulls.

The aim of this study was to verify the hypothesis that insertion/deletion (indel) polymorphisms within the promoter and intron 1 sequences of the prion protein (PRNP) gene can affect the breeding value of Holstein-Friesian bulls. The experimental material included 261 Holstein-Friesian bulls born between 1997-2002. It was shown that the polymorphism in the intron 1 (12 bp indel) sequence had a more significant effect on the analyzed traits than a polymorphism in the promoter (23 bp indel) sequence. A deletion allele within intron 1 (12del) significantly increased the bulls' breeding value for milk yield (p=0.001), protein yield (p=0.042), type and conformation (p=0.018), udder width (p=0.003), dairy character (p=0.004), and decreased days open (p=0.022). A deletion allele (23del) at the polymorphic locus of the promoter significantly decreased the bulls' breeding value for milk yield (p=0.001), udder width (p=0.029) and dairy character (p=0.033). Analysis of both alleles showed that 23del-12del haplotype increased the bulls' breeding value for udder traits: udder (p=0.008), fore udder (p=0.043) and udder depth (p=0.041), and decreased for fat content (p=0.047) and conformation traits - body depth (p<0.001), chest width (p=0.029) and rear leg set - side view (p=0.029). Also positive effect of 23del-12ins haplotype for days open (p=0.003) and days between calving and first insemination (p=0.045) was observed. [ABSTRACT FROM AUTHOR]