title: The heritability of abortion in pedigree Charollais flocks.
abstract: Foetal death, or abortion at term, in sheep is of major significance to the livestock industry, accounting for more than £24million lost per annum. We have investigated whether there is a genetic component to abortion within two flocks of pedigree Charollais sheep, one followed from 1989 to 2006, the other from 1992 to 2006. Abortion occurred at a rate of 5.74-8.78% per annum against a total mortality rate of 14-24%. By model covariate analysis we have shown that 15.5% aborting ewes went on to have one or more abortions and that this risk increased with parity (p=0.006). Heritability estimates were approximately 0.08 as calculated by SOLAR, pedigreemm and ASReml3, with sire and dam components of 0.046 and 0.048, respectively. Where the lamb was aborted, heritability estimates were highly variable according to the method employed, 0.046-0.378, with sex of the lamb being a significant covariate. This variability indicated one or more underlying, significant factors that were not measured in these analyses, potentially including infectious agents that may be involved. Nevertheless, the ASReml3 estimate (0.179) resolved to 0.074 variance attributable to the sire and 0.092 attributable to the dam, which, while not significant, was suggestive that genetic variants passed by the dam to the lamb may be of more weight than that from the sire in determining whether a lamb will abort.
authors.affiliation: School of Biology, Miall Building, University of Leeds, Leeds LS2 9JT, UK. Electronic address: rebecca.darlay@ncl.ac.uk.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Darlay
authors.affiliation: Institute of Production, Disease and Welfare, University of Glasgow, Glasgow G61 1QH, UK.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Stear
authors.affiliation: School of Biology, Miall Building, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Sam
authors.initials: S
authors.lastname: Mason
authors.affiliation: Environment and Life Sciences, University of Salford, Salford M5 4WT, UK.
authors.forename: Judith
authors.initials: J
authors.lastname: Smith
authors.affiliation: Leeds Institute of Biomedical and Clinical Sciences, St James's University Hospital, University of Leeds, Leeds LS9 7TF, UK.
authors.forename: Marie-Anne
authors.initials: MA
authors.lastname: Shaw
mesh_terms: D000034:Abortion, Veterinary / Q000235:genetics*; D000818:Animals; D005260:Female; D020022:Genetic Predisposition to Disease; D014644:Genetic Variation; D011247:Pregnancy; D012756:Sheep; D012757:Sheep Diseases / Q000235:genetics*
keywords: Abortion; Heritability; Sheep