Does the osteon morphology depend on the body mass? A scaling study on macroscopic and histomorphometric differences between cow (Bos taurus) and sheep (Ovis aries)

Abstract

The structure and geometry of bone depend on many biological and environmental factors. These factors affect the bone tissue's microstructure differently, and their interaction has not yet been fully elucidated. Our research investigated the effect of body mass on the macro- and microstructure of the compact bone. Therefore we analyzed the humerus and femur bones from females of 11 cows and 11 sheep at the age of 4–10 years. Both species have very similar dietary and locomotion patterns, but their body size and weight are very different. Within macroscopical analyzes of bones were observed ascending order of robustness index and bone diaphysis index. In both animals, plexiform and irregular Haversian bone tissues were identified in humerus and femur. Conversely, the dense Haversian tissue present only in cow above all in the femur. The most considerable interspecific osteonal difference between sheep and cow was in the osteon density, whose average value is 37% higher in the cow. The osteons of sheep humerus are almost circular, and osteons of cow femur are more elliptical. Within both species, the femoral osteons are elliptical than those of humerus. Despite the cow weighing more than 10 times the sheep, the measurements of osteons and Haversian canals, are very similar (the values of the ratio cow/sheep for these types are comprised from 1.04 to 1.86). Our findings indicate that the body mass does not affect the size of bone microstructure, probably more sensitive to other factors as a lifestyle and locomotor ability.