Articular cartilage proteoglycan metabolism in avian degenerative joint disease: Effects of strain selection and body weight

The effects of strain selection and body weight on proteoglycan metabolism and the onset of degenerative joint disease (DJD) were investigated in avia n articular cartilage. Samples from the hock joint (proximal tarsometatarsu s, PTM; distal tibiotarsus, DTT) of rapidly growing broiler fowl, fed eithe r ad libitum or on a restricted-diet, were compared with those from a slow growing, light and non-selected strain (J-line), Synthesis and degradation of proteoglycans were investigated by radioactive pulse-chase studies, dete rmination of total sulphated glycosaminoglycans and electrophoretic analysi s, By gross morphology, degenerative changes in articular cartilage occurre d solely in the DTT from ad libitum-fed broiler fowl, after 13 weeks. Diffe rences in proteoglycan metabolism were also observed, most markedly in the DTT, where the rate of proteoglycan synthesis in the ad libitum-fed group w as less than in age-matched J-line cartilage, and the proportions of both n ewly synthesised and resident proteoglycans released into the culture mediu m were greater. Results with the feed-restricted group were intermediate be tween ad libitum-fed and J-line, Electrophoretic analysis of proteoglycans in the culture media showed evidence of degradation solely in the ad libitu m-fed group, with earliest onset in the DTT, The results indicate that prot eoglycan metabolism in avian articular cartilage is similar to that in mamm alian cartilage during the development of DJD, and that the onset of cartil age degeneration is linked with excessive load bearing.