PS4-13. Pedigree and Genomic Analysis in Caspian Horses in the United States.

Abstract The Caspian horse is an ancient horse breed that was found in the mountain ranges around Iran. The breed was thought to be extinct until 1965. The breed was highly regarded by royalty and depicted pulling chariots into war in several ancient paintings. They were known for their athletic abilities and noble nature. Due to the historical importance of this horse breed this discovery was important causing immediate conservation efforts to be put into place with breeding programs and transportation of the horses among different countries. This study is being conducted at Sul Ross State University in combination with the McNair Scholar's program and is focused on the Caspian breed and plans to investigate their pedigrees and genomics of the endangered equine breed. Genomic and pedigree analysis of Caspian horses is crucial as Caspians are an endangered breed. We plan to focus on pedigree analysis, with an acute understanding of where that may take us in the future. This will help support conservation efforts by reducing inbreeding and the potential occurrences of less desirable genes or disorders. The breed pedigree analysis will highlight how the Caspian breed is doing with inbreeding/ linebreeding in attempts to preserve the breed. Due to the Caspian horse's limited population in the United States, only 15 samples were collected for genomic analysis (provided by the Equus Survival Trust). The generation of a baseline genome will provide a foundation for further work in breed preservation as well as open the door to the ability to eliminate undesirable genetic combinations. This project is currently underway, and analysis will be completed by May 2026. Through the use of the R package PurgeR, we plan to estimate the inbreeding coefficients of various lines of Caspian horses. This calculation will allow us to assess equivalent complete generations to determine the effective population size of the breeding population within the United States breeding stock. We also plan to assess the effective number of ancestors and founders of the U.S. breeding population. This data will help breeders make informed decisions to ensure genetic health and diversity in lines from a small population. To validate the pedigree-based estimates, we will use Single Nucleotide Polymorphism (SNP) data to calculate genomic inbreeding coefficients based on runs of homozygosity. We hope to continue efforts of preservation until the breed has been completely brought back from being endangered.