Evaluation of expected response to selection for orthopedic health and performance traits in Hanoverian Warmblood horses.

The research aims to understand if selecting Hanoverian Warmblood horses based on orthopedic health traits aligns with breeding for performance in dressage and jumping. The study involves evaluating relative breeding values, developing selection schemes, and assessing the response to selection across two generations. The results indicate that selection focused on orthopedic health traits could lead to improvements in both health and performance.

Methodology

• Hanoverian Warmblood horses were the subject species of this study with a sample size of 5,928 horses.
• The researchers predicted Relative Breeding Values (RBVs) for specific orthopedic health traits, including osseous fragments in fetlock (metacarpo- and metatarsophalangeal) and tarsal joints, deforming arthropathy in tarsal joints, and pathologic changes in distal sesamoid bones. RBVs are useful for estimating the genetic value of an individual horse.
• Selection schemes were developed based on total indices for radiographic findings (TIR), dressage (TID), and jumping (TIJ).
• The response to this selection was traced over two generations of horses for dressage and jumping ability, and all-purpose breeding.
• The researchers used the development of mean RBVs, mean total indices in sires, and prevalences of orthopedic health traits in their offspring to assess the response to selection.

Results

• When the researchers gave equal weight to TIR and TID, TIJ, or a combined index of 60% TID and 40% TIJ, 43% to 53% of paternal grandsires and 70% to 82% of descending sires passed selection.
• RBVs and total indices increased in the selected sires by up to 9% compared to all sires, and the prevalences of orthopedic health traits in the offspring of the selected sires decreased by up to 16%.
• When selection was conducted solely based on TID, TIJ, or TID and TIJ, between 44% to 66% of sires in the first generation and 73% to 84% in the second generation were selected, and the TID and TIJ also saw increments by 9% to 10% and 19% to 23%, respectively.

Conclusions

• The research indicates that selecting for orthopedic health traits does not drastically affect the percentage of sires selected nor the breeding progress in dressage and jumping.
• Using a selection based on TIR resulted in less prevalent orthopedic health problems in the offspring.
• The trade-off between orthopedic health and performance was found to be minor, suggesting an opportunity for balanced performance and health selection for breeding.