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The mechanical properties of horn samples from 22 hind claws with chronic laminitis were determined in adult Austrian Fleckvieh cows. The resistance to deformation was quantified as the modulus of elasticity (E). Tension tests revealed mean E values of 520 MPa for the dorsal wall, 243 MPa for the abaxial wall, 339 MPa for the axial wall and 97 MPa for the sole. E tended to be lower in laminitic horn than in sound horn in all segments tested, with the difference being largest in the abaxial wall. The mean dry-matter content (DMC) of the laminitic claws was 75.8% in the dorsal wall, 75.86% in the abaxial wall, 71.15% in the axial wall and 69.28% in the sole. These values are generally comparable to those for sound claws except in the axial wall. Further, E and DMC were only correlated in the axial wall. Chronic laminitis leads to a low resistance of claw horn to mechanical insults in the dorsal wall, abaxial wall and sole, and to the loss of a correlation between the E and DMC in these segments. The reason for these alterations is therefore not increased ingress of moisture, but must be due to changes in the microstructure, biochemical components and/or horn formation by the diseased dermis. |
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