The effect of polymorphisms of the prion-proteine-gene on fertility of ewes and weight of lambs in Merinoland- and Rhönsheep

A total of 273 Merinolandsheep with 951 lambings and 71 Rhönsheep with 182 lambings was analysed to study the association between PrP genotypes and reproductive traits. Additionally, 179 Merinolandsheep lambs and 75 Rhönsheep lambs were available to analyse the effect of PrP genotype on birth weight and early growth traits (weight at 10 week and daily gain). The Merinolandsheep showed a frequency of only 9% for ewes and 23 % for lambs for the desired ARR allele which was with 67 % for ewes and 72 % for lambs much higher within the Rhönsheep. As a result within the Merinolandsheep only a few ewes and lambs within the genotype class with ARR alleles were found, which were for statistical reasons excluded from the analysis. On the other hand within the Rhönsheep the few lambs without any ARR allele were not included in the statistical analysis. For each breed, the statistical analysis was done separately. For the reproductive traits within the model as fixed effects the genotype class (0, 1 and 2 ARR alleles), the lambing number, the year of lambing and the type of lambing (single or twins) were included and as random effect the sire of the ewe. For the lamb traits the genotype class, the sex, and the lambing type as fixed effects and the sire as random effects were used in the model. For the weight at 10 weeks the age was taken into the model as covariate. For none of the analysed traits for ewes and for lambs a significant effect of the genotype class could be found. From these results it can be concluded that a strong selection for the PrP genotype ARR/ARR will not show any correlated selection response on fertility traits in ewes or on birth weights and early growth traits in lambs.

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