Genetic parameters, genome-wide associations and potential candidate genes for additive and dominance effects of tail traits in Merinoland sheep based on whole-genome sequence data in a selection experiment.

The aim of this study was an in-depth genomic analysis for tail length (TL), tail characteristics and body measurements in the Merinoland sheep breed considering whole-genome sequence data. Genomic analyses included the estimation of genetic parameters and dominance effects, genome-wide associations for the additive and dominance component, and the annotation of potential candidate genes. We implemented a unified selection and mating experiment to create extreme lamb groups based on breeding values for TL. The 254 lambs from the mating experiment were phenotyped at birth for TL, tail circumference, and body length (all in cm), for body weight, and X-rayed to count the number of vertebrae and to identify tail abnormalities for tail fractures, axis deviations, block vertebrae, and wedged vertebrae. Heritabilities using the variant-based relationship matrix were large for the morphological measurements TL (0.85), body length (0.93), and body weight (0.85), moderate for tail circumference (0.21), and number of vertebrae (0.29), but close to zero for tail abnormalities. Dominance variance for TL explained 14.95% of the phenotypic variation, but was close to zero for the remaining tail traits. The positive breeding value correlations indicate longer and thicker tails for taller and heavier lambs. Breeding value correlations were negative between TL with block vertebrae and wedged vertebrae. Genome-wide associations for additive-genetic and dominance effects revealed 726 significant variants, which are located close to potential candidate genes. These candidate genes have known functions on skeletal growth, and regulate the development of bone structures and of vertebrae characteristics.