Genetic correlations between conformation traits and radiographic findings in the limbs of German Warmblood riding horses.

This research uses data from German Warmblood horses to investigate the genetic connections between certain physical traits and specific types of limb problems shown in X-rays. The study suggests that while selective breeding for improved conformation can be helpful, it should not be the only method used to try and reduce these limb issues, especially concerning osseous fragments in the fetlock joints.

Research Methodology

• The study used data from 20,768 German Warmblood mares and 5102 Hanoverian Warmblood horses, including both studbook inspection (SBI) information and radiography results (RR).
• The physical traits (conformation and basic quality of gaits) were scored on a scale of 0 to 10, providing 14 different SBI traits for the correlation analysis.
• The radiographic findings included in the analysis were osseous fragments in the fetlock (OFF) and hock joints (OFH), deforming arthropathy in the hock joints (DAH), distinct radiographic findings in the navicular bones (DNB), and the overall appearance of the navicular bones (RNB).
• The latter results were evaluated both as binary and quasi-linear traits.
• Genetic parameters were estimated multivariately in linear animal models using REML, considering information on 24,448 horses with SBI and/or RR records.

Findings and Implications

• The study found measurable genetic correlations between specific physical traits and certain radiographic findings, with heritability ranging from 0.09 to 0.5 for the SBI traits and 0.14 to 0.34 for the RR traits.
• Negative additive genetic correlations were observed between OFF and limb conformation, as well as the horse’s walk, and between DNB and hind limb conformation.
• There were indications of negative genetic correlations between DAH and all SBI traits, but due to the low prevalence and heritability of DAH, these conclusions need further verification.
• Positive additive genetic correlations were observed between the height of the horses at the withers (high part of the back) and both OFF and OFH, suggesting that breeding for taller horses might increase the occurrence of these conditions.
• The authors suggest that the practice of selective breeding focused on conformation traits could assist in reducing these issues, but it cannot replace possible selection against these radiographic findings, particularly with regards to OFF.