Osteochondrosis (OC) is the most common developmental orthopaedic disease in horses and represents a major problem to the horse industry. The complete mechanism of this multifactorial disease is not yet elucidated, but it is accepted that OC lesions are the result of intrinsic genetic and external factors. The aim of the present work was to evaluate the relationship between breeding management and OC. Breeding conditions were recorded, and a radiological examination was performed in 223 foals. Feeding practice and housing management were analysed in a multivariate model to determine risk factors for OC in three periods: gestation, birth to weaning and weaning to one-year-old. The major breakthrough of this study is the significant relationship between OC development and (1) the maternal nutrition during gestation and (2) the type of housing of the foals during their first year. It appears that mares fed with concentrates during gestation are more likely to produce foals that are subsequently affected by OC compared with other mares (P<0.05). Foals housed exclusively at pasture until one year of age are significantly less affected than foals exclusively housed in box or, alternatively, in box and at pasture (P<0.05). These results underline the role of the energy metabolism and the level of exercise in the aetiologic process of the disease, and help to develop preventive strategies during the crucial period of gestation to one year of age of the foal.

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Introduction: Osteochondrosis (OC) is a developmental disease in horses which has a significant impact on the horse's welfare and performance. The early disturbance in the process of endochondral ossification progresses to inflammatory and repair processes in older horses. Previously, differentially expressed genes in leukocytes of OC-affected horses have been identified. The aim of the present study is to detect age-related changes in these differentially expressed genes.Materials and Methods: The expression of OC-related genes was analysed by real-time PCR and subsequent statistical analysis (ΔΔCT) in the leukocytes of 135 Belgian Warmblood horses divided into three different age groups: <12 months (n=47), 18–24 months (n=50) >30 months (n=38).Results: Relative expression of genes of horses less than 12 months of age showed significant induction of the genes MGAT4A, PRKCG, MHCI, ApoB, ApoB3G, B4GALT6 and a significantly lower expression of the genes OAS3. Horses of 18–24 months of age, showed a significantly higher expression of the genes TBC1D9, MGAT4A, IFIH1, MHCIIa and MMP1. Horses of more than 30 months of age showed a significantly higher expression of the genes MGAT4A, HP, SECTM1 compared with their age-matched control groups.Conclusions: The study demonstrates that OC-related genes are differentially expressed in horses of different ages compared with their age-matched controls. Some of the genes may be implicated in cell signalling and differentiation as well as carbohydrate and lipid metabolism and inflammation. However, the causal relationship between the differentially expressed genes and the development and progression of the OC lesions needs to be determined.

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