Performance of Swedish Warmblood fragile foal syndrome carriers and breeding prospects.
Abstract: Warmblood fragile foal syndrome (WFFS) is a monogenetic defect caused by a recessive lethal missense point mutation in the procollagen-lysine, 2-oxoglutarate 5-dioxygenase 1 gene (PLOD1, c.2032G>A). The majority of homozygous WFFS horses are aborted during gestation. Clinical signs of affected horses include fragile skin, skin and mucosa lacerations, hyperextension of the articulations, and hematomas. In spite of its harmful effect, a relatively high frequency of WFFS carriers has been found in Warmblood horses, suggesting a heterozygote advantage. Thus, in this study our aims were to: (1) estimate the frequency of WFFS carriers in the Swedish Warmblood breed (SWB), (2) estimate the effect of WFFS carrier genotype on performance traits in two SWB subpopulations bred for different disciplines, and (3) simulate the potential effects of balancing selection and different selection strategies on the frequency of carriers. Methods: In total, 2288 SWB sport horses born between 1971 and 2020 were tested for the WFFS mutation and had estimated breeding values (EBV) for ten traditional evaluating and 50 linear descriptive traits. Results: The frequency of WFFS carriers calculated from a pool of 511 randomly selected SWB horses born in 2017 was equal to 7.4% and ranged from 0.0 to 12.0% among the whole set of tested SWB horses, starting from 1971 till 2020. The effect of the WFFS carrier genotype was significant for several EBV mainly related to movements and dressage traits and especially for horses not bred for the show jumping discipline. Using simulation, we showed that balancing selection can maintain a recessive lethal allele in populations such as the SWB breed over generations and that the frequency is expected to slowly decrease in absence of balancing selection. Finally, we showed that selection against carrier sires can result in a more rapid decrease of the frequency of the mutant allele over time. Conclusions: Further research is needed to confirm the apparent association between equine performance and the WFFS carrier genotype. Identification of such associations or new causative mutations for horse performance traits can serve as new tools in horse breeding to select for healthy, sustainable, and better performing horses.
© 2022. The Author(s).
Publication Date: 2022-01-21 PubMed ID: 35062868PubMed Central: PMC8783495DOI: 10.1186/s12711-021-00693-4Google Scholar: Lookup
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Summary
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This research study explores the presence and impact of Warmblood fragile foal syndrome (WFFS), a genetic defect, in Swedish Warmblood horses. The study found that a significant number of these horses carried the gene for this syndrome, and it suggested an apparent relationship between carrier status and performance traits.
Objective
The main goals of this study were threefold:
- To estimate the incidence of WFFS carriers in the Swedish Warmblood horse breed.
- To determine if being a carrier of the WFFS gene had any effect on performance traits for Swedish Warmblood horses bred for a variety of disciplines.
- To use simulations to understand the potential consequences of different breeding approaches on the prevalence of WFFS carriers.
Methods
The researchers examined a group of 2288 Swedish Warmblood sports horses born between 1971 and 2020. Each horse was tested for the WFFS mutation and was evaluated for ten common and 50 detailed descriptive traits.
Results
The results demonstrated that the incidence of WFFS carriers in a subset of 511 horses born in 2017 stood at 7.4%. The percentage varied within the wider set of horses, with rates between 0% to 12% from 1971 to 2020.
Another finding is that the WFFS carrier genotype markedly impacted several evaluated breeding traits affiliated mostly with movement and dressage features. This effect was particularly significant in horses that were not bred for show jumping.
Simulations
The study’s simulations showed that ‘balancing selection’, a process where genetic diversity is maintained in a population, can retain a harmful recessive gene over generations in breeds like the Swedish Warmblood. In the absence of this mechanism, however, the frequency is likely to decrease slowly.
Another outcome from the simulations was that actively selecting against sires that are WFFS carriers can result in a quicker reduction in the prevalence of the mutant gene.
Conclusions
The researchers concluded that more studies are necessary to solidly establish a link between the performance of horses and their WFFS carrier genotype. By uncovering such relationships or identifying new mutations affecting performance traits, the findings can be used in horse breeding to select healthier, more sustainable, and higher-performing horses.
Cite This Article
APA
Ablondi M, Johnsson M, Eriksson S, Sabbioni A, Viklund ÅG, Mikko S.
(2022).
Performance of Swedish Warmblood fragile foal syndrome carriers and breeding prospects.
Genet Sel Evol, 54(1), 4.
https://doi.org/10.1186/s12711-021-00693-4 Publication
Researcher Affiliations
- Department of Veterinary Science, Università degli Studi di Parma, 43126, Parma, Italy.
- Dept. of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, PO Box 7023, S-750 07, Uppsala, Sweden.
- Dept. of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, PO Box 7023, S-750 07, Uppsala, Sweden.
- Department of Veterinary Science, Università degli Studi di Parma, 43126, Parma, Italy.
- Dept. of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, PO Box 7023, S-750 07, Uppsala, Sweden.
- Dept. of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, PO Box 7023, S-750 07, Uppsala, Sweden. sofia.mikko@slu.se.
MeSH Terms
- Alleles
- Animals
- Genotype
- Homozygote
- Horses / genetics
- Mutation
- Sweden
Grant Funding
- H1147215 / Swedish-Norwegian Foundation for Equine Research
- H1847406 / Swedish-Norwegian Foundation for Equine Research
- 2020-01333 / Svenska Forskningsrådet Formas
Conflict of Interest Statement
The authors declare that they have no competing interests.
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Citations
This article has been cited 2 times.- Stefaniuk-Szmukier M, Błaszczak A, Długosz B, Musiał A, Ropka-Molik K. Surveillance of a PLOD gene variant linked to fragile foal syndrome in Silesian horses in Poland: implications for genetic monitoring and breeding strategies. J Vet Res 2025 Dec;69(4):600-602.
- Ablondi M, Eriksson S, Mikko S. Haplotype structure and heterozygosity around the fragile foal syndrome variant in Swedish Warmblod horses. Anim Genet 2025 Jun;56(3):e70022.
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