Heritabilities and genetic correlations between fetlock, hock and stifle osteochondrosis and fetlock osteochondral fragments in Hanoverian Warmblood horses.

This study investigates the genetic nature of osteochondrosis (abnormal development of cartilage on the surface of a bone) and osteochondrosis dissecans (a joint condition where filaments of cartilage flake away from the bone) in Hanoverian Warmblood horses, in an effort to identify potential breeding measures that could reduce the prevalence of these conditions.

Methodology

• The researchers used data from the X-ray exams of 7396 Hanoverian Warmblood horses. They focused their attention on the horse’s fetlock, hock, and stifle joints as these are common areas where osteochondrosis and osteochondrosis dissecans can occur.
• Genetic parameters, including heritability (the proportion of phenotypic variation attributable to genetic variation) and genetic correlations (indicating the degree of shared genetic factors), were gauged using a statistical method known as residual maximum likelihood (REML).

Findings

• The study’s findings showed moderate heritability estimates for osteochondrosis and osteochondrosis dissecans in fetlock, hock, and stifle joints, ranging from 0.16 to 0.46. The lowest heritability was found in the case of osteochondral fragments, especially in fetlock joints.
• For osteochondral fragments, specifically palmar or plantar osteochondral fragments (POFs) and dorsodistal osteochondral fragments (DOFs) in fetlock joints, heritabilities were also determined to be at a moderate level, at 0.19 and 0.22 respectively.
• A negative genetic correlation was found between palmar plantar osteochondral fragments and osteochondrosis in each joint, meaning genetic changes that increase the frequency of one cause a decrease in the other.

Implications

• The heritability estimates suggest that breeding measures could be used to reduce the occurrence of these radiographic findings. However, the variety of clinical entities requires differentiation to avoid underestimating heritabilities.
• The study’s findings will allow the recognition of OC and OCD in fetlock, hock and stifle joints, POFs of the hindlimbs, and DOFs as individual genetic traits, which could influence the success of selective breeding programs.