Biomechanical Properties of Bovine Claw Horn
Department of Morphology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, BelgiumBiosystems Engineering (Impact Factor: 1.62). 04/2006; 93(4):459-467. DOI: 10.1016/j.biosystemseng.2006.01.007
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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- "Breed differences in the micro structure of claws of German Blackhead Mutton, Merinoland and Merino Mutton, Suffolk and Gray Horned Heath sheep were identified by Kindler (1990). Franck et al. (2006) compared the numerical density as well as the diameters of the horn tubules and found the highest tubule number in the dorsal wall and the lowest in the sole (bulb). Diameters were highest in the bulb horn. "
ABSTRACT: This study compared claw conformation (length of dorsal border (DB), diagonal length (DL), dorsal angle (DA), heel height (HH), hardness) and claw horn structure (number of horn tubules, diameter of tubules medullary cavity (TC), thickness of tubules cortex (TX) and average and total horn tubules zone) of two sheep breeds. Heritabilities for these parameters were estimated and the relationship to the incidence of footrot investigated. In total, front and hind claws of 240 sheep of the two breeds Merinoland (ML; n = 142) and Rhoen sheep (RH; n = 98) were examined four times in monthly intervals. Animals were screened for footrot every second week during the study period. DL and DB, were greater in ML than in RH (P < 0.05) and greater in front than in hind claws (P < 0.05). Front claws had greater HH and DA than hind claws (P < 0.05) with the values being superior in ML compared to RH (P < 0.05). Only in ML front and hind claws differed in their hardness (P < 0.05). Only 14% of ML animals were footrot-positive. These animals showed higher values in DA (P < 0.01) and HH (P < 0.05) and shorter DL than footrot-negative ones. Heritability estimates were on a moderate level for DL (0.29-0.53) and HH (0.15–0.25), whereas lower values were estimated for DB (0.04–0.15) and DA (0.08–0.19). Hardness was not found as a possible selection trait. Regarding the claw horn structure, TC, TX and average and total tubules zone were lower in ML than in RH (P < 0.05). In RH hind claws had larger average (P < 0.05) as well as total (P < 0.05) tubules zone than front claws. Parameters of claw horn structure showed moderate heritabilities (0.36–0.57). In conclusion, the results indicated the possibility to select sheep on the basis of morphological parameters of claw conformation and claw horn structure for an improved claw quality. However, the low incidence of footrot-positive animals did not allow drawing conclusions on the relationship between the observed parameters and the incidence of footrot.
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- "Furthermore, as nanoindentation provided values of the reduced Young's modulus E r , Poisson's ratio is required to calculate Young's modulus E. However, to our knowledge, no values for Poisson's ratio of feather keratin are published. Published values of several structurally related materials range from 0.35 to 0.4 [0.4 for oryx horn (Kitchener and Vincent, 1987), 0.38 for bovine claw horn (Franck et al., 2006) and 0.35 for dry wool fibers (Fraser and Macrae, 1980)]. Although feather keratin differs from other keratin (Stettenheim, 2000), a Poisson's ratio of 0.4 [oryx horn (Kitchener and Vincent, 1987)] was utilized to calculate Young's modulus. "
ABSTRACT: Flight feathers of birds interact with the flow field during flight. They bend and twist under aerodynamic loads. Two parameters are mainly responsible for flexibility in feathers: the elastic modulus (Young's modulus, E) of the material (keratin) and the geometry of the rachises, more precisely the second moment of area (I). Two independent methods were employed to determine Young's modulus of feather rachis keratin. Moreover, the second moment of area and the bending stiffness of feather shafts from fifth primaries of barn owls (Tyto alba) and pigeons (Columba livia) were calculated. These species of birds are of comparable body mass but differ in wing size and flight style. Whether their feather material (keratin) underwent an adaptation in stiffness was previously unknown. This study shows that no significant variation in Young's modulus between the two species exists. However, differences in Young's modulus between proximal and distal feather regions were found in both species. Cross-sections of pigeon rachises were particularly well developed and rich in structural elements, exemplified by dorsal ridges and a well-pronounced transversal septum. In contrast, cross-sections of barn owl rachises were less profiled but had a higher second moment of area. Consequently, the calculated bending stiffness (EI) was higher in barn owls as well. The results show that flexural stiffness is predominantly influenced by the geometry of the feathers rather than by local material properties.
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- "The mechanical properties of keratinous biomaterials in a broad array of taxa have been examined. Some relevant experimental results on the elastic moduli with hydration effect are summarized in Table1, including those of hagfish thread (Fudge and Gosline, 2004), horse hoof (Bertram and Gosline, 1987; Douglas et al., 1996), donkey hoof (Collins et al., 1998), bovid hoof (Franck et al., 2006; Zhang et al., 2007), ostrich claw and feather (Bonser, 2000; Taylor et al., 2004), swan feather and goose feather (Cameron et al., 2003), human hair and nail (Baden, 1970; Wei et al., 2005), wool (Feughelman and Robinson, 1971), as well as antelope horn sheath (Kitchener and Vincent, 1987). Similar to antelope, other bovid animals also have horns composed of a keratinous sheath overlying a bony core (Huang and Yu, 1997). "
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.