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
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
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.
References
This article includes 28 references
- Abccb. História da Raça no Brasil. 2023.
- Charlesworth D, Willis J H. The genetics of inbreeding depression. Nature Reviews Genetics 2009;10(11):783–796.
- Willoughby J R, Ivy J A, Lacy R C, Doyle J M, DeWoody J A. Inbreeding and selection shape genomic diversity in captive populations: implications for the conservation of endangered species. PLoS One 2017;12(4).
- Santos Alves J, da Silva Anjos M, Silva Bastos M. Variability analyses of the maternal lineage of horses and donkeys. Gene 2021;769.
- Jansson M, Laikre L. Pedigree data indicate rapid inbreeding and loss of genetic diversity within populations of native, traditional dog breeds of conservation concern. PLoS One 2018;13(9).
- Rafter P, McHugh N, Pabiou T, Berry D P. Inbreeding trends and genetic diversity in purebred sheep populations. Animal 2022;16(8).
- Dias I M G, Bergmann J A G, Rezende A C C, Castro G H F. Formação e estrutura populacional do eqüino Brasileiro de Hipismo. Arquivo Brasileiro de Medicina Veterinária e Zootecnia 2000;52(6):647–654.
- Medeiros B R, Bertoli C D, Garbade P, McManus C M. Brazilian Sport Horse: pedigree analysis of the Brasileiro de Hipismo breed. Italian Journal of Animal Science 2014;13(3):p. 3146.
- López-Cortegano E. purgeR: inbreeding and purging in pedigreed populations. Bioinformatics 2022;38(2):564–565.
- Racine J S. RStudio: A Platform-independent IDE for R and Sweave. JSTOR 2012.
- Baena M M, Gervásio I C, Rocha R d F B, Procópio A M, de Moura R S, Meirelles S L C. Population structure and genetic diversity of Mangalarga Marchador horses. Livestock Science 2020;239.
- Fao F a A O. Secondary Guidelines for Development of National Farm Animal Genetic Resources Management Plans - Management of Small Populations at Risk. 1998.
- Frankel O H, Soulé M E. Conservation and Evolution. CUP Archive 1981.
- Boichard D, Maignel L, Verrier E. The value of using probabilities of gene origin to measure genetic variability in a population. Genetics Selection Evolution 1997;29(1):5–23.
- Duru S. Pedigree analysis of the Turkish Arab horse population: structure, inbreeding and genetic variability. Animal 2017;11(9):1449–1456.
- Giontella A, Pieramati C, Silvestrelli M, Sarti F M. Analysis of founders and performance test effects on an autochthonous horse population through pedigree analysis: structure, genetic variability and inbreeding. Animal 2019;13(1):15–24.
- Perdomo-González D I, Laseca N, Demyda-Peyrás S, Valera M, Cervantes I, Molina A. Fine-tuning genomic and pedigree inbreeding rates in equine population with a deep and reliable stud book: the case of the Pura Raza Espanola horse. Journal of Animal Science and Biotechnology 2022;13(1):127–214.
- Maciel F C, Bertoli C D, Neto J B, Cobuci J A, Paiva S R, McManus C M. Population structure and genealogical analysis of the Brazilian Crioula Horse. Animal Genetic Resources/Resources génétiques animales/Recursos genéticos animales 2014;54:115–125.
- Vicente A A, Carolino N, Gama L T. Genetic diversity in the Lusitano horse breed assessed by pedigree analysis. Livestock Science 2012;148(1-2):16–25.
- Hamann H, Distl O. Genetic variability in Hanoverian warmblood horses using pedigree analysis. Journal of Animal Science 2008;86(7):1503–1513.
- Stephens T D, Splan R K. Population history and genetic variability of the American Shire horse. Animal Genetic Resources/Ressources génétiques animales/Recursos genéticos animales 2013;52:31–38.
- Bozlak E, Radovic L, Remer V. Refining the evolutionary tree of the horse Y chromosome. Scientific Reports 2023;13(1):p. 8954.
- Smits K, Hoogewijs M, Woelders H, Daels P, Van Soom A. Breeding or assisted reproduction? Relevance of the horse model applied to the conservation of endangered equids. Reproduction in Domestic Animals 2012;47(s4):239–248.
- Haynes W. Effect of the popular sire. Journal of Heredity 1915;6(11):494–496.
- Álvarez I, Royo L, Pérez-Pardal L, Fernández I, Payeras L, Goyache F. Assessing losses of genetic variability in the endangered Mallorquí horse. Czech Journal of Animal Science 2010;55(10):456–462.
- Al Abri M A, König von Borstel U, Strecker V, Brooks S A. Application of genomic estimation methods of inbreeding and population structure in an arabian horse herd. Journal of Heredity 2017;108(4):361–368.
- Patterson Rosa L, Campos F A, Martin K. Demystifying the genetic origins of the Mangalarga horse through the influential stallion turbante J.O.. Journal of Equine Veterinary Science 2022;113.
- Medeiros B, Barcelos K, Da M. The Weight of Genetic Drift: A Pedigree-Based Evaluation of the Breton Horse Population in Brazil. 2023.
Citations
This article has been cited 0 times.Use Nutrition Calculator
Check if your horse's diet meets their nutrition requirements with our easy-to-use tool Check your horse's diet with our easy-to-use tool
Talk to a Nutritionist
Discuss your horse's feeding plan with our experts over a free phone consultation Discuss your horse's diet over a phone consultation
Submit Diet Evaluation
Get a customized feeding plan for your horse formulated by our equine nutritionists Get a custom feeding plan formulated by our nutritionists
