Linking early life conditions to osteochondrosis prevalence in gilts

Osteochondrosis (OC) involves the development of necrotic growth cartilage near the surface of a joint and is suggested to be associated with lameness in sows. Development of OC in pigs occurs at young age in a relatively short time frame of several weeks around 10 weeks of age. Due to this time dependency, one may wonder whether there are time dependent effects of factors or conditions associated with OC. The aim of this thesis was to assess whether OC prevalence is associated with conditions encountered in early life such as dietary restriction, floor type, conformation and locomotive characteristics (CLC), natural (auto-) antibodies (N[A]Ab), and carbohydrate levels. Indications for time dependent effects were found for dietary restriction on OC prevalence. This indicated that gilts receiving restricted feeding from 4 to 10 weeks of age and switched to ad libitum feeding until 26 weeks of age had a significantly higher prevalence of OC when compared to gilts receiving restricted feeding after 10 weeks of age. Time dependent effects of floor type were not clearly present, but gilts housed on a deep litter type system using wood shavings after weaning had a higher prevalence of severe OC when compared to gilts kept on a concrete partially slatted floor. Feed with a lower carbohydrate level increased OC prevalence compared to feed with a higher carbohydrate level. We hypothesized that the effects of dietary restriction, floor type, and dietary carbohydrate levels were mediated through loading of the joints either by, respectively, a short rapid increase in weight gain, higher incidence of play behaviors, or by an overall increased body weight. Although OC has been suggested to be associated with various CLC such as lameness, a consistent association of CLC at young age with OC at slaughter could not be found. This is likely due to CLC and OC both varying over time, making associations between the 2 entities complicated. There were indications that a component of the immune system is associated with OC as N(A)Ab against several antigens were found after weaning in association with OC. However, as with the CLC, associations with OC were not consistent over time, making it difficult to discern the exact associations between N(A)Ab and OC. To conclude, several early life conditions were found to affect or be associated with OC prevalence in gilts. This indicates that if one wants to reduce OC prevalence, one needs to start early after weaning. However, the exact implications of OC on CLC such as lameness and, therefore, welfare remain uncertain and require further studies into the long term welfare effects of OC.