Genetic Characterization of Mangalarga Marchador Breed Horses Based on Microsatellite Molecular Markers.

The research investigates genetic diversity in the Mangalarga Marchador horse breed in Brazil using microsatellite markers. The findings indicate moderate gene flow and some crossbreeding with other horse breeds, suggesting the need for a genetic breeding program to conserve the breed’s unique genetic structure.

Sample Population and Methodology

• The research involved a database of 3,193 genotyped horses, including 2,829 Mangalarga Marchador (MM) horses and smaller samples of six other breeds.
• Researchers analyzed the data using 13 microsatellite markers, molecular tools used for determining genetic diversity and population structure.
• The parameters estimated included mean number of alleles (Nm), number of rare alleles (AR), expected heterozygosity (He), F statistics, genetic distances, Hardy-Weinberg equilibrium test (HWE), and population structure.

Findings

• The MM breed revealed a mean number of alleles (Nm) of 10.85 and expected heterozygosity (He) of 0.7402. These parameters suggest the presence of significant genetic diversity within the breed.
• F statistics indicated some deviations from Hardy-Weinberg equilibrium, a state in a population where genetic variation remains constant through generations. This suggests the presence of processes such as mutation, selection, or genetic drift.
• Genetic distance analysis showed that Arabian (ARA) and English Thoroughbred (THO) breeds had greater distances with the other breeds than the distances between the Brazilian breeds (including MM) and the breeds from the Iberian Peninsula.
• Population structure analysis suggested gene flow (exchange of genetic variation) amongst the MM population and some evidence of crossbreeding with other horse breeds.

Implications

• The findings point to a need for immediate implementation of a genetic breeding program to ensure the conservation of the genetic diversity of the MM breed, potentially faced with a dilution of its genetic definition due to crossbreeding.
• Such a program would need to strive to maintain the breed’s distinctive genetic characteristics while managing its diversity and preventing potential inbreeding.