The Croatian Posavina Horse (CPH) is a native breed facing conservation challenges, yet it plays a vital role in maintaining animal genetic resources at both national and global levels. This study delves into the current status of the CPH population by analyzing its pedigree, phenotypic characteristics, and genetic structure. The findings are crucial for guiding effective conservation programs for this endangered local horse breed.
Pedigree Analysis and Population Structure
The CPH Studbook, established in 1998, contains 28,483 records. Analysis of the pedigree revealed a relatively modest depth, with a mean number of complete generations at 1.66 and equivalent generations at 2.42. This reflects the recent history of systematic breeding efforts for the breed. The generation interval was found to be approximately 8.20 years, indicating a reasonably early involvement of animals in reproduction.
Key population parameters were assessed, including the effective number of founders (fe) at 138 and effective number of ancestors (fa) at 107. The ratio of fe/fa was 1.29, suggesting a historical bottleneck effect, though not severe enough to significantly impact the population’s current genetic diversity. The average inbreeding coefficient (F) was a low 0.85%, with recent trends indicating stabilization and effective breeding program implementation. The effective population size (Ne) was calculated at 438.71, suggesting a healthy population size capable of sustaining genetic diversity if managed appropriately. The Genetic Conservation Index (GCI) averaged 4.46.
Analysis of Wright’s F statistics for living horses indicated FIS = −0.049, FST = 0.049, and FIT = 0.002 when considering sire-lines. For mare-lines, these values were FIS = −0.144, FST = 0.1281, and FIT = 0.002. The negative FIS values suggest an excess of heterozygotes within both sire and mare lines, which is a positive sign for genetic diversity.
Phenotypic Characteristics
The CPH retains its recognizable characteristics as a small-sized, cold-blooded type horse, with traces of earlier Arabian and other breed influences. Morphometric measurements showed significant sexual dimorphism. Stallions averaged 142.79 cm in height at withers, 194.28 cm in chest circumference, and 22.34 cm in cannon bone circumference. Mares were slightly smaller, with averages of 139.71 cm, 190.30 cm, and 20.94 cm, respectively. These measurements align with the breed standard and indicate a healthy development compared to historical data, likely due to selective breeding and improved nutrition.
Genetic Diversity and Microsatellite Analysis
Microsatellite analysis of 292 stallions across 29 active sire-lines revealed high genetic diversity. The mean number of alleles per locus was 7.9, with an observed heterozygosity (HO) of 0.730 and expected heterozygosity (HE) of 0.731. Polymorphism information content (PIC) values were generally high, indicating the suitability of the chosen microsatellite markers for genetic studies. Only one locus, HTG6, showed lower polymorphism.
All analyzed loci were in Hardy–Weinberg equilibrium, and the mean inbreeding coefficient (FIS) was −0.015, indicating no significant inbreeding among the stallions. Factorial Correspondence Analysis (FCA) and neighbor-joining tree visualization did not reveal distinct genetic clustering among the sire-lines, suggesting a well-mixed population and free gene flow. While a bottleneck was detected using the Wilcoxon sign-rank test, the overall high genetic diversity suggests that the breed has largely recovered.
Discussion and Conservation Implications
The findings underscore the importance of a comprehensive approach to CPH conservation, integrating pedigree, phenotypic, and genetic data. The breed exhibits valuable genetic variability and maintains its distinct phenotypic characteristics. The low inbreeding and high heterozygosity are attributed to a large gene pool, free exchange of animals among breeders, and potentially historical introgression from other breeds.
The presence of numerous sire and mare lines, coupled with a healthy effective population size, provides a strong foundation for continued conservation efforts. Maintaining the current breeding objectives, which emphasize phenotypic recognizability and adaptability, alongside rigorous genetic management, is crucial. The study suggests that the CPH has the potential to move out of the endangered category with continued appropriate management and economic affirmation. Future strategies could also consider profiling a lighter riding type if breeder interest and conservation status allow, ensuring economic viability alongside genetic preservation.
Conclusion
The Croatian Posavina Horse possesses a valuable amount of genetic variability with no significant signs of inbreeding. The breed has maintained its phenotypic recognizability and compactness, supported by a favorable number of stallion and mare lines. With appropriate breeding management and economic reaffirmation, the CPH can sustain its genetic diversity and improve its conservation status. The comprehensive data from this study will be instrumental in guiding future breeding management and conservation strategies for this important local horse breed.
