Pedigree analysis of the Turkish Arab horse population: structure, inbreeding and genetic variability.

The study aims to assess the genetic variability in the Turkish Arab horse population using pedigree data. It is the first extensive pedigree analysis of the breed in Turkey, involving data from 23,668 horses born between 1904 and 2014.

Research Methodology

• The researchers collected pedigree data for 23,668 Arab horses from the National Studbook, all born between 1904 and 2014.
• Within this dataset, a reference population (RP) of 14,838 horses representing the most recent generation was established.
• Several parameters were calculated, including demographic parameters, the inbreeding level (F), the average relatedness (AR), the effective population size (N e), the effective number of founders (f e), the effective number of ancestors (f a), and the number of founder genome equivalents (f g).

Findings

• The average generation interval for the RP was 12.2±4.6 years and the mean equivalent generations (t), the average complete generations and the mean maximum generations for the RP were 7.8, 5.4 and 12.2 respectively.
• The calculated pedigree completeness levels were 98.2%, 96.6% and 95.0% for the first, second and third known generations respectively.
• Moreover, the inbreeding level and average relatedness were 4.6% and 9.5% for the reference population.
• The study noted a high rate of inbred animals at 94.2% for the reference population.
• The number of founders and ancestors, along with the effective number of founders, ancestors, and founder genome equivalents, were 342, 223, 40, 22, and 9.6 for the RP, respectively.
• A striking disparity between the number of founders and the effective number of founders indicated a marked decrease in genetic diversity between the original founder animals and the reference population.
• The research also revealed that the contributions made by the 14 most influential founders accounted for 50% of the genetic variability in the reference population. A small group of just eight horses was responsible for creating half of the population’s genetic variability.

Implications and Conclusion

• The study provided a deep insight into the genetic variability, inbreeding and structure of the Turkish Arab horse population.
• The high inbreeding level indicates a potential risk for the breed’s resilience and survivability, suggesting the need for proper breeding management to preserve the population’s genetic diversity.
• The results demonstrated the significant impact of a small number of founders on this horse population. This can limit genetic diversity and has implications for the overall health and robustness of the breed.
• However, there was a decreased trend in inbreeding in the most recent years, which is promising for the future genetic health of the population.