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Losses of genetic diversity in the rare Xalda sheep breed due to the implementation of a selective policy including the increase of resistance to scrapie

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Authors: I. Álvarez, L.J. Royo, J.P. Gutiérrez, J.J. Arranz, I. Fernández, F. Goyache
Issue: 102-2 (139-144)
Topic: Animal Production
Keywords: Genetic variability, Genealogical information, Microsatellites, Conservation program, PrP.

The aim of this note was to assess the effect of selection to reduce sensitivity to scrapie on the genetic variability in the rare Xalda sheep breed of Asturias using genealogical and molecular information. Pedigree information comprised 1851 animals (1444 alive) at the moment of sampling. A total of 304 reproductive (or selected for reproduction) Xalda individuals were sampled and genotyped for 14 microsatellites. Genetic variability was assessed via expected heterozygosity (He; obtained from molecular information) and gene diversity (GD; obtained from genealogical information). The individuals born during the last lambing season and further selected for reproduction were identified. Losses of genetic variability in the Xalda breed were computed considering the scrapie genotype as an additional selection criterion or not. Selection against sensitivity to scrapie produces additional losses of more than 2% for He in the females. Regarding the males, the situation becomes critical because of the little available number of ARR/ARR rams. Consequences on the management of the Xalda breed are discussed.

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