Characterization of the Sarcidano Horse Coat Color Genes

Pedigree tracing to determine the origins of the modern Palomino Horse Breeders of America stock-type horse

Registration numbers for the Palomino Horse Breeders of America (PHBA) have risen with the assistance of new registration guidelines. These changes in guidelines allowed for registration of any horse with a palomino body color, including those with unknown pedigrees. While this promoted registry growth, documenting the breed's orgins from those known pedigrees making up the breed's foundation is important with the introduction of unknown pedigrees. This can be accomplished using pedigree tracing, which is of particular value for color registries as the study of coat color patterns is plagued with misunderstandings due to pedigrees with inaccurate color designations. Thus, the objective of this study was to develop an understanding of the historical origins of the modern PHBA stock-type horse through pedigree tracing. Horses (n = 460) were randomly sampled from published entries from 10 years (2012-2022) of the PHBA World Show Championship Horse Show. The All-Breed Database was utilized to obtain documentation of extended pedigrees that included uninterrupted generation-to-generation inheritance patterns of a cream dilution allele-influenced coat color. Pedigrees were traced back to the earliest recorded relative. We observed six foundation sires contributed to the modern PHBA stock-type horse with the majority (58%) tracing back to a sire named Old Fred. Two identified sires, Yellow Jacket (4%) and Cotton Eyed Joe (3%), have conflicts concerning color designation. While these results assist in documenting the breed's origins, genetic testing is required to accurately identify the cream dilution allele within the horses registered to ensure a phenotype-based solely on the cream dilution allele.

Genetic characterization of phenotypic traits in endangered Taishu horse breed and their breeding strategy

The Taishu horse is a native Japanese breed threatened with extinction. It is important to genotype the causative genes of rare phenotypes in endangered breeds because unique genetic traits might be lost unless a breeding strategy for conservation is constructed. In the present study, nine single-nucleotide variants and three indels of nine genes related to coat color, body composition, and gait were genotyped in 56 Taishu horses. Of these, only three genes were polymorphic. The observed coat color phenotypes coincided with the estimated phenotype from the genotypes, whereas black horses showed specific phenotypes that were generally black in winter but turned light brown in summer. No DNA polymorphisms in ligand-dependent nuclear receptor corepressor-like gene and very few polymorphisms in myostatin gene were identified. While means of withers height, chest circumference, cannon circumference, and body length were 122.8, 143.1, 16.9, and 130.2 cm, respectively, no relationship was found between the variants investigated and the body composition measurements. The gaited allele of doublesex and mab-3 related transcription factor 3 gene was not observed and the estimated phenotypes coincided with the observed phenotype, trot. Genotypes of coat color in the Taishu horses are essential for the construction of breeding strategies to conserve black and chestnut horses, which are much less common than bay horses. These results may help breeders construct breeding strategies to conserve rare phenotypic traits in this breed. This initiative will also be beneficial for breeding programs of other native Japanese horses, such as Noma and Miyako, whose numbers are declining.

Coloration in Equine: Overview of Candidate Genes Associated with Coat Color Phenotypes

Variation in coat color among equids has attracted significant interest in genetics and breeding research. The range of colors is primarily determined by the type, concentration, and distribution of melanin pigments, with the balance between eumelanin and pheomelanin influenced by numerous genetic factors. Advances in genomic and sequencing technologies have enabled the identification of several candidate genes that influence coat color, thereby clarifying the genetic basis of these diverse phenotypes. In this review, we concisely categorize coat coloration in horses and donkeys, focusing on the biosynthesis and types of melanin involved in pigmentation. Moreover, we highlight the regulatory roles of some key candidate genes, such as MC1R, TYR, MITF, ASIP, and KIT, in coat color variation. Moreover, the review explores how coat color relates to selective breeding and specific equine diseases, offering valuable insights for developing breeding strategies that enhance both the esthetic and health aspects of equine species.

Discrepancies between Genetic and Visual Coat Color Assignment in Sarcidano Horse

This study aimed to evaluate the discrepancies between genetic and visual coat color assignment in the Sarcidano Horse and to elucidate potential reasons. Individual DNA from 90 Sarcidano Horses was used for genetic assignment of coat color to explore the correspondence with individual forms containing phenotypical traits. The MC1R exon 1 and ASIP exon 3 have been genotyped and sequenced to obtain a picture of the coat color distribution in this breed. Surprisingly, once we compared the genetic results with the individual forms reporting the phenotypic data for each subject, a certain degree of non-correspondence between the phenotypic and genetic data in relation to coat color emerged. From the genetic analysis, Chestnuts (n = 58) resulted the most common Sarcidano Horse (n = 58), followed by a quite large number of Blacks (n = 28) and a very small number of Bays (n = 4), whereas phenotypic distribution resulted in 38 Chestnuts, 40 Bays, only 2 Blacks, and 10 Grays (without the possibility of recognizing the true color they carried). Chestnut resulted a very representative coat color, while many horses that visually identified as Bays were genetically Blacks. This discrepancy, that could be due to a variety of individual and external factors, including age, time of year, living situation and dietary condition, suggesting the importance of accurate coat color identification to ensure adequate features registration and reliable prediction of offspring's coat color.