Genetic variables of various manifestations of osteochondrosis and their correlations between and within joints in Dutch warmblood horses.

This research looked into the genetic variables of osteochondrosis in horses, displaying varied heritability estimates across different joints, with an overall heritability value of 0.23. The study suggests that the optimal approach towards selection against osteochondrosis should consider all four main joints and differentiate between bone shape alterations and fragments.

The Study

• The research team conducted a thorough study on the genetics of osteochondrosis (OC). This is a significant orthopedic developmental disorder present in several horse populations. It is typically diagnosed by signs of joint pain, tenderness, or limitation of movement.
• This study included 811 randomly chosen one-year-old horses from the Royal Warmblood Studbook of The Netherlands. These horses descended from 32 specific stallions and were assessed for OC at 28 common sites.
• Scientists assessed each site with a 5-point scoring system, differentiating between flattened bone shapes and fragments. This provided a more detailed understanding of the extent and type of OC.

Findings

• Through the examination of the joint scores, the researchers estimated the genetic variables of different OC manifestations, such as heritabilities and genetic correlations.
• The overall heritability of OC was established to be 0.23, while the heritability for flattened bone shapes was 0.08, and the heritability for bone fragments was 0.22.
• In terms of specific joint heritability, it was found to be highest in the tarsocrural joints, moderate in the metacarpophalangeal and metatarsophalangeal joints, and lowest in the femoropatellar joints. Notably, the heritability estimates for the contralateral (opposite) joint homologs were very similar.
• Moreover, a strong genetic correlation was noted between the tarsocrural and femoropatellar joints, with moderate correlations between other joints.

Conclusions

• The research results suggested a higher heritability on the observed five-point scale than when analyzing OC as a binary trait.
• The researchers concluded that selecting against OC would be most effective by considering the OC status of all key joints involved (femoropatellar, tarsocrural, metacarpophalangeal, and metatarsophalangeal joints) and distinguishing between altered bone contours and fragments. This approach would allow for more targeted and effective selection against OC in future generations of horses.