# Surveillance of a PLOD gene variant linked to fragile foal syndrome in Silesian horses in Poland: implications for genetic monitoring and breeding strategies

## TL;DR

This study tracks a genetic mutation in Silesian horses linked to fragile foal syndrome, showing a 14.6% carrier rate and emphasizing the need for genetic monitoring and careful breeding.

## Contribution

The study reports an updated and higher carrier frequency of the PLOD1 mutation in Silesian horses compared to prior studies and other breeds.

## Key findings

- The PLOD1 mutation carrier frequency in Silesian horses is 14.6%.
- The carrier frequency is higher than in Swedish Warmbloods but similar to Hanoverians and Oldenburgs.
- The findings stress the importance of genetic testing and breeding strategies to prevent fragile foal syndrome.

## Abstract

The Silesian horse is a heavy warmblood breed developed in Polish Silesia through the covering of local mares by East Frisian and Oldenburg stallions. Because of its historical significance and genetic heritage, the breed is part of a conservation programme in Poland. One of the genetic disorders of concern in warmblood horses is fragile foal syndrome (FFS), an autosomal recessive disease caused by a mutation in the PLOD1 gene (c.2032G>A). Affected foals either perish in late pregnancy or are born with severe connective tissue abnormalities, leading to early death. As carriers do not exhibit symptoms, genetic testing is crucial for responsible breeding. This study aimed to assess the prevalence of the PLOD1 mutation in the Silesian horse population.

Samples of DNA from 284 breeding horses were analysed using PCR and restriction-fragment length polymorphism and validated by Sanger sequencing.

The detected carrier frequency was 14.6%, an increase over previously reported carriage for this breed. Compared to other warmblood breeds, the carrier frequency in Silesian horses was higher than in Swedish Warmbloods, similar to the frequency in Hanoverians (14%) and also aligned with that in Oldenburg horses, from which Silesians historically derive.

The results highlight the need for continued genetic monitoring and informed breeding strategies to prevent the spread of FFS in the Silesian horse population.