Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2007
Publication Date: 10/1/2007
Citation: Evoniuk, J.M., Berg, P., Johnson, M.L., Larson, D.M., Maddock, T., Stoltenow, C.L., Schauer, C.S., Orourke, K.I., Redmer, D.A. 2007. Association between genotypes at codon 171 and 136 of the prion protein gene and production traits in market lambs. American Journal of Veterinary Research. 68(10):1073-1078. Interpretive Summary: The US scrapie control program is an integrates active and passive surveillance to detect infected flocks and a genetically based flock clean up and post exposure monitoring program based on the well established resistance of sheep with particular forms of the prion precursor gene. In addition, the federal government, the US sheep industry, and private producers use prion genotyping and selection for resistant breeding stock as a preventive tool. The success of this approach depends in part on the production fitness of scrapie-resistant sheep. In this publication, the association between prion genotype and selected production traits in lambs was examined. The study confirmed early small studies that demonstrated no deleterious effect of selection for resistant animals.
Technical Abstract: Scrapie is a transmissible spongiform encephalopathy of small ruminants for which infection is genetically controlled by commonly occurring polymorphisms in the gene encoding the normal prion protein precursor gene Prnp. Selection of sheep with the Prnp allele encoding arginine at codon 171 is remarkably effective at reducing scrapie prevalence in exposed flocks. Selection for resistant sheep is included in the joint federal state scrapie eradication program and is also used as a prevention measure and economic tool by producers without a history of scrapie. The success of these programs is based on the fitness of genetically resistant stock in production settings. In this study, a sample of nearly 1000 market lambs from two sites was examined for the association between selected growth and carcass traits and Prnp genotype. The authors report that selection for the resistant arginine171 allele, as currently prescribed by the USDA scrapie eradication guidelines, should not pose any detriment to lamb production in a commercial flock scenario. Findings from this study may in fact suggest an advantage, particularly in average daily gain, in those lambs with at least one arginine 171 allele.