Genotyping in the Brazilian Criollo Horse Stud Book: resources and perspectives.

This research evaluates the genetic variability and exclusion probability of the Brazilian Criollo Horse breed using genotypic information from the Stud Book, recommending its value for parentage establishment.

Research Overview

This study focusses on understanding the genetic makeup of the Brazilian Criollo Horse using genotyping data. The researchers analyzed data based on eight microsatellite markers from the breed’s Stud Book to understand the breed’s genetic diversity and potential for parentage determination. Two widely adopted software, namely Cervus 3.0.3 and Genepop 4.0, were used for the analysis.

Genotyping Evaluation

• An evaluation of eight microsatellite markers showed a yield of 109 total alleles, averaging around 13.6 alleles per locus.
• There were conspicuous differences between expected and observed heterozygosity (0.821 +/- 0.07 and 0.470 +/- 0.17 respectively), indicating variations from the anticipated mix of genetic traits.
• The null allele frequency of 0.284 +/- 0.199 caused some concern initially. Null alleles are a type of mutation leading to non-functioning of the gene product. However, this frequency was considered a likely outcome of the found inbreeding coefficients (0.432 +/- 0.184).
• All gene loci showed significant deviation from the Hardy-Weinberg equilibrium, a principle that states that both allele and genotype frequencies in a population remain constant from generation to generation unless influenced by specific genetic factors.
• There was documented evidence of heterozygote deficit (P < 0.0001) and genotypic linkage disequilibrium with at least one marker, indicating a reduced number of heterozygotes and the non-random association of alleles at different loci, respectively.

Polymorphic Information Content and Exclusion Probability

• The high polymorphic information content (0.798 +/- 0.088), which quantifies the discriminative power of genetic markers, can not ensure exclusion power for three gene loci (HMS7, HMS6, HTG4) above 50 percent (0.491 +/- 0.158). Exclusion power is a parameter to determine if a locus can be disregarded.
• When combined, the exclusion probability managed to reach 99.61 percent, nearly perfect. This data suggests that these markers significantly aid in determining parentage amongst this horse breed.

Conclusion

The study concluded that the performance of the markers used in the genetic analysis was excellent in providing a clear picture of the breed’s genetic status. This genotypic information from the Brazilian Criollo Horse Stud Book can significantly contribute to establishing parental relationships within this breed.