Delayed osteon formation in long-bone diaphysis of an 11-year-old giant cow with dermal dysplasia

The transverse sections of radius diaphysis in an 11-year-old giant Holstei n cow with dermal dysplasia of a collagen disorder-related skin fragility ( Cow 1), probably based on increasing turnover of the dermal collagen as rep orted previously, were morphologically and physico-chemically investigated. Cow 1 had about one and a half times as much as the body weight of normal Holstein cows, aged 5 to 6.5 years with stabilized growth. The bone samples were compared with those of a 12-year-old Holstein cow as controls (Cow 2) . It has been reported that the long-bone diaphysis of young calves and som e herbivorous dinosaurs are occupied with laminar bone showing a concentric appositional formation, and that such a laminar bone is characteristically seen during the growing period of some farm animals and large dogs that sh ow very rapid growth rates. Cow 1 had a smaller number of osteons than Cow 2 in the outer-half layer of the diaphysis, and showed an intermediate type between Cow 2 and a 1-year-old Holstein ox in the entire layers, although their bone volumes were similar among them. There were no significant diffe rences in Ca and P concentrations and the Vickers microhardness values betw een the bone matrix of Cow 1 and Cow 2. The bone-collagen fibrils of Cow 1 showed uneven diameters and a disordered arrangement. Thus, there may be so me relation in collagen formation between the bone matrix of Cow 1 and the dermis. From the remaining volume of laminar bone, Cow 1, aged 11 years, ha d probably shown growth until quite recently, so that we consider that Cow 1 became a giant animal, in the same way as some herbivorous dinosaurs.