D-loop haplotype diversity in Brazilian horse breeds

Abstract

The first horses were brought to Brazil by the colonizers after 1534. Over the centuries, these animals evolved and adapted to local environmental conditions usually unsuitable for exotic breeds, thereby originating locally adapted Brazilian breeds. The present work represents the first description of maternal genetic diversity in these horse breeds based on D-loop sequences. A D-Loop HSV-I fragment of 252 bp, from 141 horses belonging to ten Brazilian breeds / genetic groups (locally adapted and specialized breeds) were analysed. Thirty-five different haplotypes belonging to 18 haplogroups were identified with 33 polymorphic sites. Haplotype diversity (varying from 0.20 to 0.96) and nucleotide diversity (varying from 0.0039 to 0.0239) was lower for locally adapted than for specialized breeds, with the same pattern observed for FST values. Haplogroups identified in Brazilian breeds are in agreement with previous findings in South American samples. The low variability observed mainly in locally adapted breeds, indicates that, to ensure conservation of these breeds, careful reproductive management is needed. Additional genetic characterization studies are required to support accurate decision-making.

Genetic analysis of maternal and paternal lineages in Kabardian horses by uniparental molecular markers

“…The haplotype diversity of Kabardian (0.980) is similar to that of the additional investigated Asian horses or higher. That also applies to comparison with other breeds like Arabian (0.784 and 0.962), Thoroughbred (0.883 and 0.942), Kazakh (0.977), Chinese (0.978 and 0.989) as well as Brazilian (varying from 0.200 to 0.944) horses (Zhang et al, 2012;Ianella et al, 2017;Othman et al, 2017). However, the Kabardian horse has a huge genetic variability in its maternal lineages representing a diverse origin and a longstanding history, which is in agreement with recently published microsatellite analysis (Duduev et al, 2014).…”

Low transmission rates of Equine infectious anemia virus (EIAV) in foals born to seropositive feral mares inhabiting the Amazon delta region despite climatic conditions supporting high insect vector populations

“…Although originally geographically isolated by the island environment, these unique horses have recently been interbred with other horse breeds imported into the area to improve the size, posture and appearance. Unfortunately, most horse breeders have prioritized these phenotypic characteristics, without taking into account the features required for adaptation to the hostile environment and therefore the current interbreeding practices are becoming a major threat to the genetic integrity of the Marajoara horse [2,7,8]. The Puruca horse is another highly specialized breed found on Marajó Island that is under an even greater threat from inbreeding programs because the original population comprised of only a comparatively small number of individuals.…”

“…The Puruca horse is another highly specialized breed found on Marajó Island that is under an even greater threat from inbreeding programs because the original population comprised of only a comparatively small number of individuals. This breed was generated by breeding Marajoara horses to Shetland ponies and selecting individuals with a maximum standard height of 1.18 m. Modern breeding programs select for larger animals and thereby undermine the major phenotypic characteristic of the breed [2,7,8].…”

Low Transmission Rates of Equine Infectious Anemia Virus (EIAV) in Foals Born To Seropositive Feral Mares Inhabiting the Amazon Delta Region Despite Climatic Conditions Supporting High Insect Vector Populations

“…Although originally geographically isolated by the island environment, these unique horses have been interbred with other horse breeds recently imported into the area, to improve the size, posture and appearance, once the most horse breeders have prioritized the phenotypic characteristics, without taking into account the adaptation to the hostile environment. Unfortunately this practice is becoming a major threat to the genetic integrity of the Marajoara horse breed [2,7,8]. Another highly specialized breed found on Marajó Island is the Puruca horse.…”

“…Another highly specialized breed found on Marajó Island is the Puruca horse. This was generated by breeding Marajoara horses to Shetland ponies and selecting individuals with a maximum standard height of 1.18 meters and they suffer an even greater threat, because it constitutes a very small population and the crossbreeding has resulted in the progressive replacement of this one to a bigger animal, mischaracterizing the main pattern of the breed [2,7,8]. Therefore, the equid population of Marajó Island contains distinctive, rare horse breeds that should be preserved because they possess genetic characteristics uniquely associated with adaptation to the tropical environment of the Amazon River Delta.…”