DIFFERENCES IN PRODUCTION TRAITS BETWEEN SCRAPIE RESISTANT AND SCRAPIE SUSCEPTIBLE EWES

Scrapie is one of several transmissible spongiform encephalopathies (TSE) including bovine spongiform encephalopathy (BSE). The apparent transmission of BSE to humans in the United Kingdom resulted in a call for eradication of all TSEs in food producing animals. In the United States, scrapie has been detected only in sheep possessing alleles of the prion protein with glutamine (Q) or histidine (H) at codon 171, both reported as Q. Incidence of scrapie infection is rare when animals possess at least one allele for arginine (R) at 171. The objective of the present study was to determine if production traits differed between scrapie resistant (QR and RR) and scrapie susceptible (QQ) animals. Historic records of the Univ. of Wyoming purebred ewe flock were analyzed for evidence of production advantage to scrapie susceptible ewes. Lambing records from purebred Columbia (n=240), Hampshire (n=325), Rambouillet (n=227), and Suffolk (n=277) ewes with known genotype at codon 171 were analyzed for differences in birth-type, birth weight, adjusted weaning weight and total kg of lambs weaned per ewe lambing. In addition, influence of lamb genotype on birth weights and adjusted weaning weights was determined from the 2002 lamb crop (n=356). Suffolk ewes with QQ genotype gave birth to more (P < 0.001) lambs than QR ewes (1.8 ± .06 vs 1.2 ± .13, respectively). However, QQ Suffolk ewes weaned less (P = 0.07) total kg of lamb than QR ewes (63.2 ± 1.1 vs 70.2 ± 2.7, respectively). Although, birth weights from Rambouillet ewes tended (P = 0.09) to be influenced by ewe genotype, differences were not noted at weaning or in total kg of lambs weaned. Production traits of Columbia and Hampshire ewes did not differ by ewe genotype. There was no influence of lamb genotype (P > 0.34) on birth weight or adjusted weaning weight for any of the breeds analyzed. In conclusion, the scrapie resistance status of the ewe may influence birth-type and weight, but these differences do not appear to influence ultimate lamb production.