The objective of this study was to analyse associations between ovine prion protein genotypes and milk production in Comisano dairy sheep. Prion protein genotypes were available for 838 ewes and 232 rams. The test day records were analysed with a mixed linear model that included flock, parity, days in milk interval and PrP genotype as fixed effects, and ewes and residuals as random effects. The frequencies of scrapie resistance alleles ARH, AHQ and ARR were 0.0285, 0.0275 and 0.3935 and the frequencies of scrapie susceptible alleles ARQ and VRQ were 0.5108 and 0.0397, respectively. No significant associations were found between the prion protein genotypes and milk performance. The results indicate that a program designed to increase resistance to scrapie in Comisano breed should not affect milk yield and, therefore, can be incorporated into a breeding programme for milk improvement. Nevertheless, implementation of a breeding programme for resistance to scrapie should also consider the inbreeding rate in the population and possible negative effects of intensive selection on fitness traits and other important breed characteristics.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume , , 02.10, 2006
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