Chronic progressive lymphoedema in Friesian horses: suggestive phenotype of affected horses and genome-wide association study

Background: Chronic progressive lymphoedema (CPL) is a disabling condition affecting various draft horse breeds, including Friesian horses. Hypothesis: The high incidence of CPL in Friesian horses suggests a genetic component and a predisposing phenotype. Animals: For the genomic study, 26 affected and 19 control horses were evaluated. Body measurements were taken from 28 affected and nine control Friesian horses. Methods and materials: Axiom® Equine Genotyping Array with a total of 307,474 single nucleotide polymorphism (SNPs) was used for the case/control genome-wide association study (GWAS). Height, weight and leg measurements (seven different body measurements) were obtained and compared between groups. Results: No significant associations were identified with the GWAS. There were significant differences (P < 0.05) in gaskin length measurements between CPL-affected horses and controls. Conclusion: The current study suggests that the potential genetic contribution to CPL in Friesian horses is complex and may include other SNP-associated factors. Significantly increased gaskin length of affected horses suggests a phenotype prone to developing CPL.