Individual-based assessment of population structure and admixture in Austrian, Croatian and German draught horses.

The research focuses on understanding the population structure and the extent of interbreeding among different draught horse breed populations in Austria, Croatia and Germany, utilizing genetic data from microsatellite loci. The data reveals that certain populations have greater genetic diversity and effective population size, especially those in less intensively farmed regions. The study also shows a clear separation between different groups of horse populations, mostly based on their geographical locations.

Study Design and Methods

• The researchers analyzed the conservation status of various Austrian, Croatian and German draught horse populations, including the Noriker Carinthians, Noriker Salzburg, Croatian Coldblood, Posavina horse, Altmarksish Coldblood, Black Forest horse, Mecklenburg Coldblood, Rhenish German Draught horse, Saxon Thuringa Coldblood, Schleswig Draught horse, South German Coldblood.
• This was done using genotypic data from 30 (effectively 27) microsatellite loci – specific, repeated portions of DNA that are highly variable, making them useful for genetic fingerprinting of individuals and populations.

Findings and Interpretations

• The research found that horse populations in less intensively farmed regions had a higher genetic diversity and estimated effective population size than other populations examined in the study. This suggests that farming intensity could be a factor impacting the genetic diversity and population size of the draught horses.
• The Principal Component Analysis (PCA), a statistical method used to simplify complex genetic data, separated the populations into five distinct groups based on their genetics. The groups appear to be influenced by geography and political factors.
• The ‘Noriker’ group (NC, NS and SG) and the ‘Rhenish’ group (A, M, R, and ST) were the most distinctive genetically. The ‘Croatian’ group was at the center of the PCA plot, indicating a higher level of genetic overlap with other groups. The Black Forest and Schleswig populations were outliers compared to the other groups.
• A Bayesian analysis, another statistical method, further revealed differentiation among populations. For instance, the South German Coldblood could be differentiated from the Austrian Noriker population. This analysis also showed some level of interbreeding between the Croatian Coldblood and Posavina horse populations.

Implications and Applications

• The research offers valuable insights into the genetic structure and diversity of draught horse populations in parts of Europe, providing actionable information for efficient conservation decision-making.
• These findings can inform strategies to maintain genetic diversity and population health, which is crucial given the drastic decrease in the number of draught horses over the last five decades.
• Further research might extend this kind of analysis to other horse populations, and investigate the factors influencing genetic diversity and population structure in more detail.