title: Statistical tools to detect genetic variation for a sex dimorphism in piglet birth weight.
abstract: Sex differences in birth weight contribute to within-litter variability, which itself is connected to piglet survival. Therefore, we studied whether the sex difference in piglet birth weight is a genetically variable sex dimorphism. For that purpose a linear mixed model including sex-specific additive genetic effects was set up. A hypothesis testing problem was defined to detect whether these genetic effects significantly differ between sexes. In a second step, the effect of sex-linked genes was studied explicitly by partitioning the additive genetic effects into autosomal and gonosomal effects. Furthermore, a definition of heritability for the sex difference of a randomly chosen pair of littermates with opposite sex was given. The proposed models were applied separately to a Landrace and Large White data set. Significant genetic variability for the sex dimorphism was found in Landrace (P = 0.03) but not in Large White (P = 0.10). Heritability estimates were at 3 to 5% depending on the model. The X-chromosomal genetic variation was not significant (P > 0.18) at all, whereas the Y-chromosome significantly (P < 0.01) contributed to the genetic variation in Landrace with a corresponding SD of 34 g. It can be concluded that the sex dimorphism of piglet birth weight is genetically variable and a potential target of genetic improvement.
authors.affiliation: Leibniz Institute for Farm Animal Biology (FBN), Genetics and Biometry, Wilhelm Stahl-Allee 2, 18196 Dummerstorf, Germany. wittenburg@fbn-dummerstorf.de
authors.forename: D
authors.initials: D
authors.lastname: Wittenburg
authors.forename: F
authors.initials: F
authors.lastname: Teuscher
authors.forename: N
authors.initials: N
authors.lastname: Reinsch
mesh_terms: D000818:Animals; D001724:Birth Weight / Q000235:genetics*; D005260:Female; D014644:Genetic Variation; D008297:Male; D012727:Sex Characteristics; D013223:Statistics as Topic; D016019:Survival Analysis; D013552:Swine / Q000235:genetics* / Q000502:physiology*; D014960:X Chromosome; D014998:Y Chromosome