The relationship of standing up of warmblood foals and the prevalence of osteochondrosis, between farms.
Gezelle Meerburg, A.R.D.
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Osteochondrosis (OC) is a commonly diagnosed and clinically important joint disorder that is defined as a focal disturbance of enchondral ossification. The pathogenesis is multifactorial, but in most recent literature the failure of blood supply to the growing cartilage has been seen as a factor of major importance. Doubts about heritability of OC became clear when different joints appeared to be involved at different ages, so environmental factors are likely. Cartilage injury (with fragmentation) due to pressure changes when the leg slips, has been observed. This fragmentation can occur directly when a leg slips, or indirectly due to avascular necrosis caused by injury of the juvenile circulation. Between 5 and 8 months, the developing cartilage is susceptible for these injuries. We tested the hypothesis that there is an association between the way of standing up in foals and the development of OC. We observed the standing up behavior of 45 warmblood foals between the age of 6 to 9 months at five different farms, with different housing / bedding. Foals were observed using surveillance tube cameras, and stored on VHS videotapes (3-4 hours/day; total 24 h per farm). We scored whether there was a normal stand up (NS) or a slipping limb (SL). The standing up was scored by means of a predetermined ethogram. The prevalence of OC was determined using a mobile x-ray machine and standard criteria (A=OC absent, B-E=OC present). A two-way between groups analysis of variance was performed on different moments (OCD 5 months and 12 months), to explore the relationship between the prevalence of OCD, management factors and slipping legs. OCD was divided in two groups: 0 (OCD absent) and 1 (OCD present). The farms were divided on management factors into two groups: 0 (Low Risk), 1 (High Risk). The first ANOVA was performed with OCD results of 5 months. The relation between slipping legs and the prevalence of OCD was not statistically significant, p= 0,423. But there was a significant relation between farms and slipping legs, p= 0.004; however the effect size was small (partial eta squared = 0,231). The second ANOVA was performed with OCD results on 12 months. The relation between slipping legs and the prevalence of OCD was not statistically significant, p= 0,514. But there was a stronger significant relation between farms and slipping legs, p= 0.001; however the effect size was small (partial eta squared = 0,246). There was no significant relation between the prevalence of OCD and the sliding ratio. But high risk farms have significant more slipping foals than low risk farms. Further investigation is needed to prove the relation between sliding and the development of OCD.