Genome-Wide Association Studies Reveal Susceptibility Loci for Digital Dermatitis in Holstein Cattle.
Authors: Lai Ellen, Danner Alexa L, Famula Thomas R, Oberbauer Anita M
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Digital Dermatitis Susceptibility in Holstein Cattle Digital dermatitis represents a significant welfare and economic challenge in dairy cattle, yet its genetic basis remains poorly understood. Researchers used genome-wide association studies across four commercial dairies, genotyping 214 Holstein cows (85 with digital dermatitis lesions, 129 controls) with high-density SNP panels and analysing three distinct phenotypes: binary case status, quantitative lesion burden per trimming event, and recurrence (animals with ≥2 episodes versus controls). Statistical models identified susceptibility regions on chromosomes 2, 7 and 20 harbouring genes implicated in epidermal barrier function, immune response and tissue repair—findings that align with digital dermatitis's multifactorial pathology involving bacterial infection, environmental stress and host defence mechanisms. Whilst the identified loci showed small individual effects relative to substantial environmental influence, the SNP variants demonstrated sufficient predictive accuracy to potentially support genomic selection strategies, though larger validation cohorts are essential before implementing breeding programmes based on these markers. For practitioners, these results suggest that genetic predisposition to digital dermatitis exists and varies among individuals, supporting the integration of genomic information with established management protocols (housing, hygiene, footbathing) to reduce disease incidence in susceptible bloodlines.
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Practical Takeaways
- •Genetic susceptibility to digital dermatitis has been identified and mapped, offering potential for selective breeding to reduce disease incidence in dairy herds
- •Multiple loci with small individual effects and strong environmental influences suggest that management practices remain critical alongside any genomic selection strategies
- •Future validation with larger sample sizes may enable genomic testing to identify carrier animals for herd health planning
Key Findings
- •GWAS identified QTL regions on BTA2 associated with binary and recurrent digital dermatitis phenotypes
- •QTL regions on BTA7 and BTA20 associated with quantitative phenotype (average number of lesions per hoof trimming)
- •Candidate genes in identified regions relate to epidermal integrity, immune function, and wound healing
- •SNP predictors demonstrated high predictive value for digital dermatitis susceptibility in the cohort studied