Analysis of the Pedigree and Ancestors of the Cutting Population of the Quarter Horse Breed.

The research article evaluates the genetic diversity and influential ancestors in the population of Brazilian Quarter Horses participating in cutting events. The study found that the genetic diversity of these horses is derived from a small number of influential ancestors, which may lead to a narrowing of their genetic base.

Methodology and Data Analysis

• The researchers collected data from 1,590 elite horses that were born between 1970 and 2015 and competed in cutting from 1981 to 2018.
• These data came from the pedigree file, which contained 5,832 animals that were born from 1834 onwards.
• The quality of the information in the pedigree file was computed by understanding the number of known generations and the generation interval.
• The genetic diversity measures such as the inbreeding coefficient, relatedness coefficient, and individual increase in inbreeding were reported to be low.
• The number of effective animals in the population, known as the effective population size (N), was 136 horses.

Results on Genetic Diversity and Influential Ancestors

• The paper defined the effective numbers of ancestors and founder genomes by considering the probability of gene origin.
• A total of 1,852 founders and 899 ancestors were recorded in the population.
• About 10, 50, and 100 key ancestors explained about 39.2%, 67.9%, and 91.6% respectively, of the overall genetic diversity of the population.
• The study determined five most influential ancestors which largely influenced the genetic composition of the current population. These horses were Doc Bar, Peppy San Badger, Freckles Playboy, Poco Lena, and High Brow Cat, amounting to 30.7% of the population’s marginal genetic contributions.

Implications and Recommendations

• The study found that a small group of ancestors could be held responsible for the genetic diversity of the current Brazilian Quarter Horse population engaging in cutting.
• This dependence on a limited number of ancestors could lead to decrease and narrowing of its genetic base.
• In order to mitigate such risk, the study suggested increasing the number of breeding animals and ensuring directed mating using ancestors from diverse origins.