A case of multiple assignments (paternity/maternity) in an equine-out breeding system.

The research article discusses a successful implementation of a DNA marker-based system to determine the lineage of farm-bred horses, even in the absence of recorded mating activities or traditional breeding logs.

Introduction to Parentage and Breeding Issues in Horses

• In traditional horse breeding setups, lineage and parentage might get obscured due to numerous reasons such as unregistered mare-foal pairs at weaning, or multiple stallions mating freely with a group of mares.

The Role of DNA Markers

• Emerging technologies in genetic testing have made it possible to determine the paternity and maternity of foals using DNA markers.
• Microsatellite systems and biochemical polymorphisms are two common forms of genetic markers used in DNA testing.
• Microsatellite systems are DNA sequences that are prone to genetic variation and can provide a unique genetic blueprint.
• Biochemical polymorphisms are genetic variations leading to observable, inherited characteristics that remain stable in a population.

Purpose and Setup of the Study

• The aim of the study was to assess the effectiveness of a particular set of codominant markers along with a likelihood-based approach to determine parentage in domestic horses.
• The test environment consisted of ten mares that were freely mated with two stallions, resulting in nine foals. However, no registration of mare-offspring pairs was maintained, thereby simulating the issue at hand.

Method and Analysis

• The genetic typing of the horses was done using 12 microsatellite systems and four biochemical polymorphisms.
• The parentage evaluation process was carried out by the CERVUS program, a software tool used for assignment of parentage in animal populations through likelihood-based statistical calculations.
• This method relies on the principles of mendelian genetics, which is applied to the genotypic data of the mares, stallions, and respective offspring to postulate the most probable parent-offspring relationships.

Outcomes and Conclusion

• Successful determination of maternity was achieved in eight cases, while paternity was determined for all foals.
• The researchers concluded that the combination of the selected set of codominant markers and likelihood-based approach is a valuable tool for resolving parentage assignments in domestic horses, especially in challenging circumstances.