By Horse Sport Ireland / HSI
Photography: HSI

This study was conducted in collaboration with researchers from Teagasc, South East Technological University, the University of Agriculture in Krakow, and Texas A&M University. It focuses on the identification of horses with autosomal abnormalities using the SNP genotypes collected from Irish sport horses during the parentage verification process.
The research, titled “Detection of two horses with chromosome 27 trisomy using single nucleotide polymor-phism chip genotypes”, has been published open-access in the journal Animals and is available to read HERE.
Autosomal trisomy is a rare genetic disorder caused by the presence of an extra chromosome. While well-known in humans (e.g., Down syndrome [trisomy 21], Edwards syndrome [trisomy 18], Patau syndrome [trisomy 13]), its occurrence in horses is uncommon but can lead to developmental abnormalities, infertility, and reduced life expectancy.
This study represents the largest population-level screening for autosomal trisomy ever conducted in horses, analysing 17,078 animals. From a subset of 6,601 juvenile horses, two Irish Sport Horse colts were identified with trisomy of chromosome 27. One of these was examined and showed no obvious physical abnormalities, but the diagnosis was confirmed via cytogenetic analysis.
The findings estimate that at least 3 in every 10,000 live foal births may be affected by autosomal trisomy—an often-undiagnosed condition without genetic screening. For high-value breeding horses, the economic impact of undetected abnormalities related to fertility or development could be significant.
Horse Sport Ireland and its research partners hope this study will raise awareness of the value of routine genomic screening for chromosomal abnormalities, particularly where studbooks are already using SNP-based parentage verification...

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