Researchers have pinpointed the genetic origins of some body traits in Lipizzaners, in a step towards exploring and understanding the genetic architecture of conformation in horses.
The Lipizzan breed is considered a Baroque saddle horse, attributable to some well-known Italian and Spanish founder animals born in the 18th century.
Between 1776 and 1945 Arabian horses were also introduced, affecting the conformation of the head, neck, withers and extremities.
Currently, the lighter type Lipizzan horses are associated with higher proportions of Arabian admixture and have a more concave head and more prominent withers.
Consequently, there is relatively large phenotypic variation in the Lipizzan horse, making it an ideal model to explore conformation differences in the horse in a genome-wide association study.
Annik Gmel and her fellow researchers writing in the journal Scientific reportsthese conformation traits are important selection criteria in equine breeding, as they describe the horse’s external aspects, such as height, joint angles and shape.
“However, the genetic architecture of conformation is not well understood, as data from these traits consist mostly of subjective assessment scores,” they said.
In their study, they performed genome-wide association studies on two-dimensional shape data from 229 Lipizzan horses, including 102 females and 127 males.
Samples were collected for genetic analysis. The conformational traits were based on a single photograph taken from each horse’s flank, in an open position.
The photographs were digitized and physical landmarks drawn to be entered for analysis, along with the genetic data.
Based on these data, the study team identified significant quantitative trait loci (a region of DNA associated with a specific phenotype or trait that varies within a population) associated with crested neck on equine chromosome 16 within of the MAGI1 gene and type, differentiating heavily from light horses on chromosome 5 within the POU2F1 gene.
Both genes have been previously described to influence growth, musculature and fat deposits in sheep, cattle and pigs.
They also identified another suggestive quantitative trait loci on chromosome 21, close to the PTGER4 gene, associated with human ankylosing spondylitis, for shape differences in the back and pelvis (cockroach back versus swing back).
Further differences in the shape of the back and abdomen were suggestively associated with the RYR1 gene, involved in central muscle weakness in humans.
Discussing their findings, the authors said the study revealed several new quantitative trait loci associated with conformation in the Lipizzan horse.
The horse-shaped space model employed in the study is an efficient, high-throughput phenotyping method for inferring objective information about different aspects of equine conformation, they said.
“Based on this method, it becomes possible to derive objective conformation traits of hundreds or thousands of horses independently of the judges of the herd, which simultaneously improves the quality and quantity of data for genetic analyses.
“Furthermore, shape-derived conformation traits can be clustered across breeds and thus support cross-breed comparisons.
“However, there are currently two main limitations: the horses’ posture when analyzing a single photograph and the association of the principal components with conformation, which remains subjective.
“Excluding the effect of posture, standardizing the position of the head and limbs during the photographic shot, or using the average of different forms of the same horse photographed in different postures, principal components associated with differences in conformation should result.
“Further studies, including larger sample sizes, whole genome sequencing, and different breeds, will improve our understanding of the functional genomics of reported quantitative trait loci.”
The study team included Gmel, with the University of Zurich and the Swiss agricultural science agency Agroscope; Gottfried Brem, of the University of Veterinary Medicine in Vienna; and Markus Neuditschko, with Agroscope and the University of Veterinary Medicine Vienna.
Gmel, AI, Brem, G. & Neuditschko, M. New genomic insights into the conformation of Lipizzan horses. Sci Rep 13, 8990 (2023). https://doi.org/10.1038/s41598-023-36272-4
The study, published under a Creative Commons licensecan be read Here.
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