Regional Heritability Mapping of Age-dependent Loci Affecting Growth Traits in Scottish Blackface Lambs

Descriptors of growth derived from fitting the Gompertz curve to longitudinal live weights for 735 Scottish Blackface lambs were analysed using Regional Heritability Mapping to identify genetic regions with significant effects on growth. Evidence for loci affecting predicted growth rates and weights at distinct time points was seen on several chromosomes. Three loci on two chromosomes were mapped for age at maximum growth rate and seven regions on five chromosomes had significant associations with predicted growth rates and live weights at the suggestive level (P<2.30x10^-3). QTL significance and effects varied with age, with longitudinal QTL for growth rate often occurring earlier than for live weight. Irrespective of the methodology used to dissect loci affecting growth, the longitudinal nature of the trait, i.e. its evolution over time, needs to be taken into account, especially for genomic predictions at different growth stages.