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The Weight of Genetic Drift: A Pedigree-Based Evaluation of the Breton Horse Population in Brazil.
Abstract: The genetic diversity of Breton horses in Brazil is a critical concern, mainly due to the small population size and low number of births per year. Given that the inbreeding was overlooked by breeders for multiple generations, we estimated the genetic diversity of this population utilizing pedigree-based measures of population diversity. A total of 1394 six-generation pedigrees representing the full population of registered Breton horses in Brazil defined a total population (TP, = 2679), with horses born between 2000 and 2022, reproductively active and alive, as reported by the breed association, representing the reference population (RP, = 731). Using the R package , we estimated inbreeding coefficient ( ), maternal inbreeding coefficient ( ), paternal inbreeding coefficient ( ), individual reproductive values, number of equivalents to complete generations (), and unbiased ancestral inbreeding coefficient (). We established the equivalent complete generations (ECG), effective population size (), total number of founders (), effective number of founders (), total number of ancestors (), effective number of ancestors (), founder genomes (), and the inbreeding coefficient estimated with effective population size () and generation numbers () ( ), as well as / and / ratios for the RP. The RP inbreeding levels have stabilized, although they are still significantly rising by generation (), and the / ratio strongly suggests genetic drift. Pedigree-based analysis demonstrates that only five stallions have sired 52.83% of the RP individuals, which along with the value of 36.73 implies that the observed inbreeding can be arising from patrilines. Our results suggest that observed inbreeding is due to Popular Sire Effect, highlighting the importance of monitoring breeding schemes and genetic diversity to maintain health.
Copyright © 2024 Bruno B. Medeiros et al.
Publication Date: 2024-08-23 PubMed ID: 39220466PubMed Central: PMC11364472DOI: 10.1155/2024/4714077Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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This research study investigates the genetic diversity of the Breton horse population in Brazil, using pedigree data to draw estimates. The study focuses on understanding if inbreeding, due to a small population size and low birth rate, influences the genetic diversity within this horse breed.
Study Methodology
- The study involved an examination of 1394 six-generation pedigrees of the registered Breton horses in Brazil. The total population defined was 2679, composed of horses born between 2000 and 2022, who were reproductively active and reported as alive by the breed association.
- The researchers used the R software package to calculate various measures, including the inbreeding coefficient, maternal and paternal inbreeding coefficient, individual reproductive values, number of equivalents to complete generations, and the unbiased ancestral inbreeding coefficient.
- The study also calculated various statistical measures of population genetics – equivalent complete generations (ECG), effective population size, total number of founders, effective number of founders, total number of ancestors, effective number of ancestors, founder genomes, and the inbreeding coefficient estimated with effective population size and generation numbers.
Key Findings
- The researchers found that even though the inbreeding levels of the reference population have stabilized, they are still rising significantly by generation.
- A statistical measurement called the “F”/”Ne” ratio strongly suggests a genetic phenomenon known as ‘genetic drift’, which is a random fluctuation in the frequency of the appearance of a gene variant in a population.
- Pedigree analysis revealed that only five stallions have fathered 52.83% of the reference population individuals, which points towards the existence of the ‘Popular Sire Effect’. This may mean that the inbreeding observed could be arising mainly from the paternal side.
Conclusion and Implications
- The research concludes that observed inbreeding within the Breton horse population in Brazil is largely due to the ‘Popular Sire Effect’, suggesting that a small number of males are fathering a disproportionately large number of offspring.
- This finding stresses the importance of constantly monitoring breeding schemes and genetic diversity within populations, particularly for breeds with very small populations like the Breton horse. This is fundamental for maintaining the health of the population and reducing the risk of genetic disorders.
Cite This Article
APA
Medeiros BB, Barcelos KMC, Andrade MO, Cristina da Paz Carvalho M, Miranda VR, de Oliveira Maia K, Reinhardt S, Patterson Rosa L.
(2024).
The Weight of Genetic Drift: A Pedigree-Based Evaluation of the Breton Horse Population in Brazil.
Vet Med Int, 2024, 4714077.
https://doi.org/10.1155/2024/4714077 Publication
Researcher Affiliations
- Department of Agriculture and Industry Sul Ross State University, Alpine, TX, USA.
- Escola de Veterinária e Zootecnia Universidade Federal de Goias, Campus Samambaia, Goiânia, Brazil.
- Escola de Veterinária e Zootecnia Universidade Federal de Goias, Campus Samambaia, Goiânia, Brazil.
- Escola de Veterinária e Zootecnia Universidade Federal de Goias, Campus Samambaia, Goiânia, Brazil.
- Escola de Veterinária e Zootecnia Universidade Federal de Goias, Campus Samambaia, Goiânia, Brazil.
- Escola de Veterinária e Zootecnia Universidade Federal de Goias, Campus Samambaia, Goiânia, Brazil.
- Superintendência do Serviço de Registro Genealógico da Raça Bretã Associação Brasileira de Criadores do Cavalo Bretāo, Sao Paulo, Brazil.
- Department of Veterinary Clinical Sciences College of Veterinary Medicine Long Island University, New York, NY, USA.
Conflict of Interest Statement
Kate M. C. Barcelos is associated with the Brazilian Association of Breton Horse Breeders (BABHB) as a Technical Counselor. Susana Reinhardt is employed as Inspector Superintendent by the BABHB. All other authors have no conflicts of interest.
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