Biomechanical Properties of Bovine Claw Horn

Department of Morphology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium
Biosystems Engineering (Impact Factor: 1.37). 04/2006; DOI: 10.1016/j.biosystemseng.2006.01.007

ABSTRACT Inadequate properties of concrete floors in cattle houses seem to be the primary cause of most claw problems, resulting in economic losses and impaired animal welfare. Many claw diseases are sequels of an extreme local overload. In this paper, the mechanical strength of bovine claw horn is studied.The average Young's modulus E determined in bending and compression using a test velocity of 1 mm/min was 382 MPa for horn from the dorsal wall of the bovine claw, 261 MPa for horn from the abaxial wall and 13·6 MPa for bulb horn. There is a significant difference in Young's modulus, hence in stiffness, between dorsal and abaxial wall horn. The average yield stress was 14·3 MPa for dorsal wall horn and 10·7 MPa for abaxial wall horn in a three-point bending test, and 56·0 MPa for bulb horn in a compression test on samples with 100 mm2 surface area and 4 mm height. The registered average Poisson's ratio ν was 0·38. Histological observations could not explain the biomechanical differences between the dorsal and abaxial wall horn. The number of horn tubules per mm2 was smaller and the diameter of the tubules larger in bulb horn than in wall horn.In future research, the yield stress of the horn will be related with the maximum pressures that can occur between cattle claw and concrete floor.

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    ABSTRACT: Bovine horn is composed of a sheath of keratin overlying a bony core. Previous studies of the bovine horn sheath have focused mainly on its morphology and compositions. In the present paper, we performed a series of uniaxial tension, three-point bending, and fracture tests to investigate the structural and mechanical properties of the horn sheaths from subadult cattle, Bos taurus. The effects of hydration on the mechanical properties were examined and their variations along the longitudinal direction of the horn sheath were addressed. Scanning electron microscopy of the fracture surfaces showed that the horn sheath has a layered structure and, more interestingly, the laminae have a rippled appearance. The Young's modulus and tensile strength increase from 850 MPa and 40 MPa at 19% water content to 2.3 GPa and 154 MPa at 0% water content, respectively. The Poisson's ratio of the horn sheath was about 0.38. The critical stress intensity factor was about 4.76 MPa m1/2 at an intermediate hydration (8% water content), greater than that at 0% water content (3.86 MPa m1/2) and 19% water content (2.56 MPa m1/2). The bending properties of the samples varied along the length of the horn. The mean flexural moduli of the specimens in the distal, middle and proximal parts were about 6.26 GPa, 5.93 GPa and 4.98 GPa, respectively; whereas the mean yield strength in the distal segment was about 152.4 MPa, distinctly higher than that in the middle (135.7 MPa) and proximal parts (116.4 MPa). This study deepens our understanding of the relationships among optimal structure, property and function of cattle horn sheaths.
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