Multiple-trait selection for radiographic health of the limbs, conformation and performance in Warmblood riding horses.

The research article involves a study of multi-trait selection in Warmblood riding horses, using data from 26,434 German Warmblood horses. The traits under focus were related to radiographic health, conformation, and performance. The study confirmed the possibility of improving multiple traits simultaneously through single- or multiple-trait selection, although certain traits, like free jumping ability, only saw progress with performance-specific selection.

Study and Methodology

• This research focused on multiple trait selection which is crucial in genetic optimization catering to horsing needs like radiographic health, physical conformation, and performance capacity.
• 26,434 German Warmblood horses, born between 1992 and 2001, were analyzed in detail for such a genetic study.
• Information gathered included standardized radiological examination results of 5155 Hanoverian Warmblood horses, studbook inspection conformation evaluations of 20,603 mares, and performance evaluations from mare performance tests on 16,098 horses.
• The team carried out multivariate genetic analyses. Parameters were estimated using restricted maximum likelihood (REML), and relative breeding values (RBV) were predicted using best linear unbiased prediction (BLUP) within multivariate linear animal models.

Findings: Heritability Estimates

• Heritability estimates were obtained for four radiographic health traits, three conformation traits, and five performance traits.
• Radiographic health traits like osseous fragments in fetlock and hock joints, deformations in hock joint arthropathy and distinct radiographic findings in navicular bones showed heritability between 0.15 and 0.35 post liability scale transformation.
• Traits like front and hind limb conformation, withers height, walk, trot, canter, rideability, and free jumping demonstrated heritabilities ranging from 0.09 to 0.49. Additionally, they showed genetic correlations with OFF, OFH, DAH, and DNB from -0.53 to +0.52.

Study Analysis: Single and Multiple Trait Selection

• The research then bifurcated sire selection based on RBV or combinations of RBV. Selection for individual traits or traits from one of the three trait groups were considered as single-trait selection, with selection for traits from more than one group being multiple-trait selection.
• Selection modes were compared using expected selection response after one generation. This response was calculated as the relative change in the prevalence of radiographic findings or the mean conformation/performance scores in the offspring of selected sires compared to the offspring from all sires.

Research Outcomes

• The study showed a significant decrease in the prevalence of certain radiographic traits (30% to 57% for single-trait selection and 14% to 29% for multiple-trait selection), which connotes improvement in radiographic health.
• On the other hand, conformation and performance scores showed up to a 4% improvement.
• Despite improvements in general traits, genetic progress in regards to free jumping ability and style could only be achieved by single- or multiple-trait selection with a specific focus on jumping performance.