The effects of selective breeding against scrapie susceptibility on the genetic variability of the Latxa Black-Faced sheep breed

Abstract

-Breeding sheep populations for scrapie resistance could result in a loss of genetic variability. In this study, the effect on genetic variability of selection for increasing the ARR allele frequency was estimated in the Latxa breed. Two sources of information were used, pedigree and genetic polymorphisms (fifteen microsatellites). The results based on the genealogical information were conditioned by a low pedigree completeness level that revealed the interest of also using the information provided by the molecular markers. The overall results suggest that no great negative effect on genetic variability can be expected in the short time in the population analysed by selection of only ARR/ARR males. The estimated average relationship of ARR/ARR males with reproductive females was similar to that of all available males whatever its genotype: 0.010 vs. 0.012 for a genealogical relationship and 0.257 vs. 0.296 for molecular coancestry, respectively. However, selection of only ARR/ARR males implied important losses in founder animals (87 percent) and low frequency alleles (30 percent) in the ram population. The evaluation of mild selection strategies against scrapie susceptibility based on the use of some ARR heterozygous males was difficult because the genetic relationships estimated among animals differed when pedigree or molecular information was used, and the use of more molecular markers should be evaluated. genetic variability / scrapie / Manech / Latxa / sheep

Ovine progressive pneumonia provirus levels are unaffected by the prion 171R allele in an Idaho sheep flock

“…171R has no effect on Salmonella resistance [21]. Finally, pedigree examination in Laxta Black Faced-type Navarra sheep showed no overall negative effect [52]. …”

Diversidad genética en ovinos (Ovis aries) Asblack de Lima, Perú, utilizando marcadores microsatélites

“…Los resultados de este estudio permitirán establecer al ovino Asblack como una raza oriunda del país, permitiendo elaborar criterios de mejora genética (ovinos con dos crías mínimo y corderos con mayor peso) para mejorar la rentabilidad y facilidad de manejo de los animales. Alfonso et al, 2006). Para ello, el volumen de cada marcador en la amplificación fue estandarizado y agrupado para ser utilizados en sistemas multiplex (es decir, que en una misma reacción se amplifican varios marcadores, de acuerdo con su tamaño de pares de bases y a su temperatura de anillamiento) y en sistemas simplex (Cuadro 1).…”

Genetic variability following selection for scrapie resistance in six autochthonous sheep breeds in the province of Bolzano (northern Italy)

“…25 November 2015) and intends to urge, but not to force, the use of rams with resistant genotype to reduce the presence of undesirable PRNP alleles in Italian sheep populations, to contribute to the creation of “low risk flocks” and to protect human and animal health. However, resistant genotypes are often present in the population with a low frequency so that, using a restricted number of rams for selection programmes could lead to a potential bottleneck, with a negative impact on genetic variability and productive characteristics of Italian ovine breeds, especially for rare or endangered breeds (Alfonso, Parada, Legarra, Ugarte, & Arana, 2006; Álvarez, Gutierrez, Royo, Fernandez, & Goyache, 2009).…”