ARS | Publication request: EFFECTS OF PRION HAPLOTYPE ON GROWTH AND CARCASS TRAITS IN SHEEP

Submitted to: Midwestern Section of the American Society of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 27, 2004
Publication Date: September 1, 2005
Citation: Isler, B.J., Freking, B.A., Heaton, M.P., Thallman, R.M., Leymaster, K.A. 2005. Effects of prion haplotype on growth and carcass traits in sheep [abstract]. Midwestern Section of the American Society of Animal Science. 83(Suppl. 2):44-45

Technical Abstract: Within the sheep industry, there is concern about potential antagonistic correlated responses of economic traits due to intensive selection for scrapie-resistant haplotypes of the prion gene. The objective was to test for associations of prion haplotypes with growth and carcass traits in a F2 Dorset x Romanov population (n = 418), segregating at the callipyge locus. Animals were haplotyped at prion codons 136, 154, and 171 to determine scrapie susceptibility status, and genotyped at six flanking microsatellite markers to determine breed of origin of the prion region of ovine chromosome 13. A comprehensive set of growth, carcass shape, and composition traits were collected. Data were analyzed using a model consisting of fixed effects of year, sex, and callipyge genotype, random effects of sire, and six covariates corresponding to probabilities that an animal inherited a specific prion haplotype of either Dorset or Romanov origin. For carcass traits, the model also contained the linear and quadratic effects of chilled carcass weight as a covariate, along with the interaction between callipyge genotype and linear and quadratic terms. Within each breed of origin, contrasts between the resistant haplotype (ARR) and the average effects of the other prion haplotypes (ARQ, AHQ, VRQ) were tested to estimate effects of selection for ARR. Of the 21 traits analyzed, the only significant contrast was for carcass length in Romanov, where the ARR haplotype was associated (P = 0.035) with increased carcass length. This study is the first to account for breed of origin while investigating haplotype associations in a F2 population. This study provides little, if any, evidence of associations between prion haplotypes and growth and carcass traits.