Sheep & Goats

Exploring the genetic architecture of fleece shedding in sheep

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Abstract

Sheep production systems oriented towards meat or milk production often generate coarse wool (25-40 μm fibre diameter) as a by-product, which has limited value in high-quality apparel markets. Over the past decade, global prices for coarse wool have declined markedly, while the cost of wool harvesting (shearing) in Australia has increased by more than 200% over the last 25 years. Consequently, producers are seeking alternative strategies to reduce shearing costs, including the introduction of genetic material from breeds that naturally shed their fleeces into established terminal and maternal lines. Fleece shedding is shown to be a highly heritable trait; however, its underlying genetic architecture remains poorly understood. The objective of this study was to identify possible genomic regions and candidate genes associated with shedding to enable greater accuracy of genomic predictions and inform future selection strategies. A total of 11,690 lambs (1 year) animals with phenotypes and genotypes were analysed. Shedding was visually scored during the period of peak expression on a five-point scale, where 1 is completely shed and 5 is completely woolly. Genomic analyses were performed using GCTA software to estimate variance components, chromosomal heritabilities, and regional heritabilities using overlapping sliding windows of 100 SNPs with 50% overlap. Key genomic windows were defined as those explaining ≥2% of the phenotypic variance. Genome-wide association studies (GWAS) were conducted using a Bonferroni-corrected significance threshold of −log10(p) = 6.08 (p = 8.3 à— 10⁻⁷), based on 60,349 SNPs retained after quality control. Fixed effects included birth-rearing type (lambs), contemporary group (flock, year of birth and shedding year of measurement), days since the winter solstice, and the three main breed components derived from breed structure analysis. The heritability of fleece shedding was high, estimated at 0.54 (±0.02) in lambs and 0.58 (±0.02) in adults. Chromosomal heritability estimates indicated that chromosomes 3, 8, 13 and 23 contributed disproportionately to trait variance, with estimates ranging from 0.05 to 0.08 (±0.01). Regional heritability mapping identified key genomic windows on chromosomes 3, 13 and 23, with individual windows explaining up to 4% of the phenotypic variance. The GWAS identified 55 and 24 SNPs surpassing genome-wide significance thresholds in lambs and adults, respectively. The top-associated variant on chromosome 23 explained approximately 2.1% of the phenotypic variance in lambs and 1.8% in adults, supporting a moderate gene effect influencing fleece shedding. This study provides a large-scale genomic analysis of fleece shedding in sheep, confirming that the trait is highly heritable and potentially influenced by a small number of regions with moderate to large effects, alongside additional polygenic variation. Incorporating identified SNPs or regional genomic weights into breeding programs may improve genomic prediction accuracy and facilitate selection for low maintenance, shedding sheep.

Keywords: 2026

How to Cite:

Smith, E., Keiller, J., Kelly, M., Brown, D. & Walkom, S., (2026) “Exploring the genetic architecture of fleece shedding in sheep”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2285169. doi: https://doi.org/10.31274/wcgalp.23635

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