Characterisation of Claw–floor Contact Pressures for Standing Cattle and the Dependency on Concrete Roughness
ABSTRACT Inadequate properties of concrete floors in livestock buildings seem to be an important cause of cattle lesions. High local pressures on claw tissues may contribute to damage of the claw. Monitoring of foot-to-ground pressure distributions may provide insight in the relation between high local pressures and foot lesions.In the current research, the pressure distribution of the foot-to-ground contact area was recorded using thin film tactile sensors. During the experiments, the sensor was located between previously prepared bovine claws and concrete samples with different surface roughness. The measurement procedure permitted a gradual increase in the vertical load on the claws at a test bench, while at the same time the contact area and the pressure distribution could be registered. Five different levels of surface roughness were obtained by finishing fresh concrete samples with a metal float, a wooden float or a brush, and by washing the concrete surface to two different degrees.The results showed a clear increase in contact area with increasing pressure. The abaxial wall and bulb of the claws had the major load-bearing function. The metal-floated concrete resulted in the largest contact area and the lowest pressures, while the washed concrete resulted in much smaller contact areas and higher pressures. Other finishing methods gave intermediate results.The maximum pressure under a load of 4 kN was about twice as high on a wooden-floated or lightly washed surface (around 40 MPa), compared to a metal-floated surface (around 20 MPa). On the severely washed out surface, the maximum pressure was even four to five times higher. This may indicate a higher risk on claw lesions due to local overload.
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ABSTRACT: The interaction between bovine claws and a concrete floor with defined roughness and friction coefficients is described using a finite element model. The model was built by using x-ray tomography scanner images of an unloaded fore and hind bovine claw. These images were used to reproduce the geometry of the claw horn capsule, which was used to create a finite element model. Young's moduli of 382, 261, and 13.6 MPa were attributed to the dorsal wall horn, abaxial and axial wall horn, and bulb horn, respectively. Poisson's ratio was set at 0.38. The horn was considered an isotropic elastic material. The model was completed by introducing a rigid support that simulated a concrete floor. The floor was moved to establish contact with the claw and was loaded with a force of 2 or 6 kN. The top border area of the horn capsule was fixed, but angular rotations were allowed. With this model, the effect of varying floor roughness and claw-floor friction on contact pressures and von Mises stresses in the claw horn could be evaluated. This was demonstrated by simulating the contact between the claw models and a smooth and rough floor with a center-line roughness value R(a) of 0 or 0.175 mm, respectively, either without friction or with a static coefficient of friction of 0.75 and a dynamic coefficient of friction of 0.65. Contact pressures ranged from 2.14 to 27.55 MPa. The roughness of the floor was the main determinant in subsequent contact pressures. Maximum von Mises stresses were registered in the claw sole and were mostly between 5.04 and 16.44 MPa, but could be higher in specific situations. The variables claw (fore or hind) and floor (smooth or rough) had significant effects on the contact pressures; in addition, the floor resulted in significantly different von Mises stresses in the claw horn. The variable friction (frictionless or with friction) had a significant effect on the von Mises stresses. The load did not result in significantly different contact pressures and von Mises stresses because of the large increase in contact area with the exerted load.Journal of Dairy Science 02/2008; 91(1):182-92. · 2.57 Impact Factor
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ABSTRACT: Several studies have shown that foot lesions and clinical lameness occur before first calving and develop further during the lactation period. Lameness may cause production losses, but the relationship between foot lesions, particularly in the claw horn, and lameness in heifers is unclear. The objectives of this study were to describe the development of and evaluate the relationship between lameness and foot lesions in Danish Holsteins before and after first calving. In a longitudinal study, 147 heifers were examined for lameness and foot lesions 2-5 times over an 18-month period. Lameness was assessed by means of a visual locomotion score and foot lesion severity was recorded. The prevalence of a locomotion score 3 was 25% before calving, and 90% at approximately 250 days in milk (DIM). Prevalence of moderate to severe sole haemorrhage (SH) was 27% before calving and 56% at 250 DIM, and that of moderate to severe white line lesion (WLL) 44% before calving with a peak of 70% at 200 DIM. There was one case of white line abscess but SH was seen throughout the entire study period. Digital dermatitis (DD) was prevalent prior to first calving (15%) and peaked at 39% at 0-100 DIM. Heel horn erosion (HHE) occurred in almost all cows (93-100%) and was strongly correlated with DD (r=0.51). The correlation coefficient between SH and WLL was also high (0.42). The relatively high correlations between WLL and both DD and HHE were more surprising (0.38 and 0.35, respectively), those between SH and both DD and HHE were moderate (around 0.18). Interdigital dermatitis was significantly correlated with both HHE and DD, but completely unrelated to SH and WLL. The overall average locomotion score increased by about one-half of a score unit from 1 month prior to calving until 250 DIM, with a large difference between herds, although this was unsurprising as cows may alter their locomotion pattern with management factors (e.g. floor properties). DD and WLL were both associated with a locomotion score > or = 3 but of the cows with severe WLL there was no clear association between a locomotion score > or = 3 and DD. The highest locomotion scores occurred among cows with DD but without WLL.The Veterinary Journal 09/2008; 182(1):50-8. · 2.42 Impact Factor
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ABSTRACT: Inadequate properties of concrete floors in cattle houses are a major cause of claw problems, resulting in economic losses and impaired animal welfare. Many claw diseases are sequels of an extreme local overload due to high floor roughness or are caused by the indirect effects of the slipperiness of the floor. In this paper, the roughness of the concrete floor, the frictional interactions between bovine claw and floor and the relation between roughness and frictional properties, are studied.Concrete floor samples were made with five different finishing methods. Their roughness was determined by measuring the heights of the ‘peaks and valleys’ of the surface with a high-precision laser beam. The smoothest surface was the sample finished with a metal float (average surface roughness Ra=0·080 mm) and the roughest surface occurred with the heavily sandblasted sample (average surface roughness Ra=0·296 mm). Their roughness was also approximated with the ‘sand-patch’ method: the texture depth was calculated by dividing a fixed volume of fine dry sand by the surface area of the circle-shaped sand patch. Again the smoothest surface appeared to be the sample finished with a metal float (texture depth=0·19 mm) and the roughest surface was the heavily sandblasted sample (texture depth=0·59 mm). The sand-patch method appeared to be a reliable way of assessing the roughness of the floor.The static coefficient of friction μstat and the dynamic coefficient of friction μdyn between bovine claw models and dry and wet floors were determined by using the ‘drag method’ (a loaded bovine claw was dragged using a hand-operated winch over a flat floor sample while the tensional force was recorded). The five concrete floor panels with different roughnesses were used, but also two types of synthetic floor coverings (mat and mattress) were added to the test. The static coefficient of friction on dry floors varied between 0·60 (mattress) and 0·79 (mildly sandblasted concrete); the dynamic coefficient of friction ranged between 0·47 (mattress) and 0·69 (heavily sandblasted concrete). In wet circumstances only three floor types were tested. The static coefficient of friction varied between 0·65 (metal-floated concrete) and 0·80 (heavily sandblasted concrete) while the dynamic coefficient of friction yielded values between 0·56 (metal-floated concrete) and 0·69 (heavily sandblasted concrete). Significant differences were found between the floor types, but these were mainly due to the values measured on the metal-floated concrete, the mattress and the mat. Only in dry circumstances did the fore claws produce significantly higher coefficients of friction than the hind claws. The effect of the floor type on the coefficients of friction was in all cases many times higher than the effect of the claw itself. The static and the dynamic coefficients of friction in wet conditions were found to be larger than the same coefficients in dry conditions.The skid or slip resistance was measured separately, on wetted surfaces, with the skid-resistance tester (SRT) pendulum. The values found ranged between 20·2 (metal-floated concrete) and 49·6 (mattress). Significant differences between the floor types were found.Significant correlations were found between the static and the dynamic coefficients of friction, in dry and wet conditions, and the roughness values Rx and the texture depth. Significant correlations were also found between the SRT values and the roughness values Rx. Significant correlations were found only between the dynamic coefficients of friction and SRT values.The measured coefficients of friction were all higher than the required coefficients of friction, hence the tested floor samples provided enough resistance against slip.Biosystems Engineering. 01/2007;