Abstract
Genetic diversity and maternal ancestry line relationships amongst a sample of 96 Cleveland Bay horses were investigated using a 479bp length of mitochondrial D-loop sequence. The analysis yielded at total of 11 haplotypes with 27 variable positions, all of which have been described in previous equine mitochondrial DNA d-loop studies. Four main haplotype clusters were present in the Cleveland Bay breed describing 89% of the total sample. This suggests that only four principal maternal ancestry lines exist in the present-day global Cleveland Bay population. Comparison of these sequences with other domestic horse haplotypes (Fig 2) shows a close association of the Cleveland Bay horse with Northern European (Clade C), Iberian (Clade A) and North African (Clade B) horse breeds. This indicates that the Cleveland Bay horse may not have evolved exclusively from the now extinct Chapman horse, as previous work as suggested. The Cleveland Bay horse remains one of only five domestic horse breeds classified as Critical on the Rare Breeds Survival Trust (UK) Watchlist and our results provide important information on the origins of this breed and represent a valuable tool for conservation purposes.
Highlights
The Cleveland Bay is one of only five domestic horse breeds listed as critical (< 300 breeding females) in the Rare Breeds Survival Trust Watchlist, making it one of Britain’s oldest and most at-risk native horse breeds
We present the mitochondrial DNA (mtDNA) D-loop sequencing of a sample of 96 Cleveland Bay horses and describe the haplotypes found in the breed
The haplotypic diversity (h) calculated for the breed is significantly lower than that determined for the majority of other domestic equines (h = 0.7973) [12]
Summary
The Cleveland Bay is one of only five domestic horse breeds listed as critical (< 300 breeding females) in the Rare Breeds Survival Trust Watchlist, making it one of Britain’s oldest and most at-risk native horse breeds. The breed is thought to have been established in the seventeenth century from crosses between pack horse or “Chapman” mares, known to have been bred by monastic houses in the North-East of the UK, and newly imported hot-blooded Arabian, Barb or Mediterranean stallions, to produce an early example of what is known as a warmblood [1]. Cleveland Bays flourished throughout the eighteenth-century achieving world renown as coaching and driving horses [2]. The Cleveland Bay Horse Society (CBHS) was formed in 1884 and the first stud book was produced with pedigrees dating back to 1732 [2]. The first stud book was officially closed in 1886 and the breed has maintained a closed stud.
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