Degenerative joint disease in poultry--differences in composition and morphology of articular cartilage are associated with strain susceptibility.

The morphology and basic biochemical composition of articular cartilage from two strains of fowl were examined. Broiler breeder fowl are considered susceptible to degenerative joint disease (DJD); histological examination of one-year-old broiler breeders showed in some samples, articular cartilage thinning, fibrillation and chondrocyte cluster formation, features considered typical of DJD. Examination of similar samples from laying strain fowl showed only minor age-related changes such as some slight cartilage thinning and very mild fibrillation. The articular cartilage from the broiler breeder birds was significantly more hydrated with a higher uronic acid content than that of the laying strain birds. In addition, unloaded articular surfaces such as the proximal humerus had significantly higher amounts of uronic acid than the loaded cartilage surfaces of the proximal tarsometatarsus and the distal tibiotarsus; this suggested that the joint loading may have a role in any biochemical differences found between joints and between strains of fowl. These findings concur with other reports in mammals that showed increased hydration and uronic acid in association with early DJD and in models of osteoarthritis (OA). Thus, despite some differences between avian and mammalian articular cartilage, studies on avian DJD may give insights into mammalian disease.