| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
* Department of Veterinary Anatomy;
Department of Farm Animal Health; and
Department of Equine Sciences, Faculty of Veterinary Medicine,Utrecht University, P.O. Box 80158, 3508 TD Utrecht, The Netherlands
Institute of Agricultural and Environmental Engineering, 6700 AA Wageningen, The Netherlands
|| Faculty of Civil Engineering and Geosciences, University of Technology, 2600 GA Delft, The Netherlands
Corresponding author: P. P. J. van der Tol; e-mail: R.vanderTol{at}vet.uu.nl.
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
|---|
Key Words: dairy cattle • lameness • horn • biomechanics
Abbreviation key: GRF = ground reaction force
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
|---|
During standing or walking ground reaction forces (GRF) are exerted to the claw by the floor. The vertical component of this GRF is distributed over the contact area of the claws of a limb in a way that depends on the shape of the claws and the way the claw is placed on the floor. In turn, the vertical force distribution between lateral and medial claws and over the contact area of each claw determines the degree of local compression of the horn and underlying tissues. If cows with deformed claws walk on a hard floor it is easy to see how contact areas become reduced and pressure concentrations induced. Although the average pressure may stay within acceptable limits, local pressure concentrations may cause tissue overloading. This may on the one hand lead to horn fracturing and the opening up of infection routes and, on the other hand, cause damage to the corium, resulting in haematoma and abnormal horn formation (Toussaint-Raven et al., 1985; Greenough and Weaver, 1997; Blowey et al., 2000).
Previous work showed that during standing pressure concentrations occur at the bulb area of the lateral hind claw; this region of the bovine claw is known to be susceptible to injuries (van der Tol et al., 2002). However, during walking the total load applied on a limb can be more than twice as high (Scott, 1988), and a limited area of the claw may carry this load. There is no information available of how these loads are distributed over the potential weight-bearing area of the claw. Moreover, at certain moments during the stance phase of the step-cycle the weight applied on the supporting limb is exerted on a relatively small area, for example at heel strike or at push off.
The aim of this study is to determine the GRF and to measure the magnitude and distribution of the average and maximum pressures exerted to the contact area of the claws of dairy cattle, while walking on a flat, relatively hard surface. The hypotheses are tested that the vertical GRF and the pressures are equal for the fore and hind limbs, the vertical GRF is equally divided over both claws of a foot and that the pressures applied to each foot are equally distributed over its contact area. These dynamic measurements are now possible with a new pressure distribution plate (Footscan) firmly assembled on a (Kistler) force plate simultaneously sampling with a high spatial resolution and at high frequency.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
|---|
The pressure/force measuring system consists of a pressure distribution plate and a force plate sampled simultaneously (250 Hz). The pressure distribution plate (Footscan Scientific Version, RSscan International, Olen, Belgium) has a 976 mm x 325 mm measuring surface, containing 8192 conductive pressure-sensitive polymer sensors. These sensors measure vertical force only. Because the size of the sensors is known (0.39 cm2), the pressures can be determined automatically. This plate was embedded in an aluminium plate, which was solidly assembled on the force plate (Type Z4852/c, 600 mm x 900 mm, Kistler Corp, Winterthur, Switzerland). The force plate measures the vertical, longitudinal, and transverse components of the GRF. The assembly was placed level in a concrete pathway. The pathway and measuring apparatus were covered with a 5 to 6 mm thick rubber mat to provide enough frictional force to allow normal locomotion.
Each trial had a standard duration of 4 s. Per measurement 8192 (sensors) x 1000 (samples) data points were collected. The threshold level was set at 5 N/sensor to discard noise-related data. All above-threshold values were color-coded. The values for one step were linearly distributed over 256 available colors between the threshold (blue) and the maximum value (red). The Footscan Pressure plate uses directly the output (vertical GRF) of the Kistler Force plate for calibration. The sum of the vertical forces applied to all individual sensors of the pressure plate was automatically adjusted to the total vertical force registrated by the Kistler force plate. The force plate was calibrated with the aid of a heavy weight as prescribed by the manufacturer.
Measurements and Data Processing
The cows were repeatedly walked down the path, lead by an experienced handler to control the direction of locomotion. A measurement started at initial contact of the fore foot touching the pressure plate. The acquisition time of 4 s provided enough time to measure both the fore and hind limb of one side of an animal in a single trial. The trials continued until eight measurements for each limb had been recorded.
When processing the data, we observed that in some measurements not only the fore and hind limbs at the side of interest, but also an opposite fore or hind limb was standing on the force plate, but not on the pressure plate. These measurements had to be discarded, as the on line calibration procedure between the force and pressure plate (see above) would lead to erroneous results. From the eight consecutive measurements the first five technically correct measurements were analyzed.
The step cycle of a limb during walking can be described as a weight-bearing phase and a non-weight-bearing phase, respectively, the stance and the swing phase. The stance phase starts with the foot landing on the ground and ends after the push off when the foot is lifted from the ground (Leach, 1993; Schamhardt, 1998). During the stance phase the forces due to locomotion are exerted by the foot to the ground (Figure 1a
). With the aid of these GRF recordings, several characteristic moments can be described. During the stance phase of each individual limb, five of these moments were automatically selected to perform the analysis upon. These moments were called: heel strike, maximum braking, midstance, maximum propulsion, and push off. They were defined as follows:
|
Parameters.
Consider Fi an above-threshold vertical force, applied to the ith sensor of the pressure plate. As is the surface of each sensor. The following parameters were determined during the five moments of the stance phase:
Fi (Fi > 5 N) of the lateral claw, Fi (Fi > 5 N) of the medial claw. n(Fi > 15 N) x As
Statistical Analysis
The data consisted of measurements on four variables (Fv, A, Pav, and Pmax) at five moments during the stance phase (factor Time), for the left and the right limbs (factor Asym) and for the fore and the hind limbs (factor Fore-hind). In addition, for variable Fv a distinction could be made between the vertical force exerted to the lateral and to the medial claws (factor Claw). The data matrix was complete; each cell contained data of nine cows. The value for each individual cow was the average value of its five steps. An analysis of variance (general linear model, repeated measures; performed with the statistical package SPSS, SPSS Inc.) with the factors time, asym, and fore-hind was performed separately for the variables A, Pav and Pmax. For the variable Fv, the factor claw was also included. Although the average values for (paired) left and right limbs were almost equal, a certain amount of variance might be explained by asymmetry. Therefore, the highest and the lowest value of the limb pair were assigned to the categories "high" and "low" of a factor called Asym.
For A, Pav, and Pmax, the hypotheses were tested separately that the variables had equal values for all limbs at each moment. For Fv, in addition, the hypothesis was tested that the vertical GRF were equally distributed between the medial and lateral claw. Both the effects of factors and the interactions between factors were considered to be significant at P < 0.05. For factors that interacted significantly, post-hoc-tests were performed either to analyze differences in Time, Asym, or Fore-hind.
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
|---|
; the yellow vertical lines indicate the five moments at which the force and pressure distributions were analyzed. The longitudinal GRF (red line) shows a negative peak in the first half of the stance phase (a braking, decelerating force, directed backward), becomes zero at midstance and shows a positive peak at the second half of the stance phase (a propulsive force, directed forward). In Figure 1b an example is shown of the change of the pressure distribution in time for the fore and hind limbs. The force and pressure distribution and their change over time are somewhat different for the fore and hind limbs. The interindividual variation in the forelimbs appeared to be higher than in the hind limbs.
In general, at heel strike the forelimb (Figure 1b) lands on the bulb area of the lateral claw and to a lesser extent on the bulb area of the medial claw. After heel strike, both claws remain more or less subjected to the same vertical force (as can be observed by the center of pressure between both claws), mainly at the bulb area and at the walls. The sole is loaded lightly, as can be seen from the characteristic sickle-shaped claw print (Figure 1b). From midstance to maximum propulsion, the load shifts somewhat toward the medial claw. At push off the forces are equally distributed, loading the anterior parts of the wall and sole.
At the hind limbs (Figure 1b) the forces during heel strike are exerted mostly (> 95%) to the outer side of the lateral claw. From maximum braking to maximum propulsion the vertical load shifts towards the medial claw. However, the greater part of the force remains exerted to the lateral claw, in particular to its sole and bulb. At push off, the forces are exerted more or less equally to the anterior part of the wall and sole of both claws.
Vertical Ground Reaction Forces (Fv)
For all limbs the vertical component of the GRF increases until midstance and decreases until push off. The maximum vertical GRF (averaged over left and right limbs) at the hind limb was less (2444 N) then at the forelimb (3324 N). These forces amounted to, respectively, 37 and 51% of the BW. The magnitude of Fv was significantly different for the four investigated factors, e.g. Asym, Fore-hind, Time, and Claw (Table 1). All first-order interactions between these four factors were also statistically significant, except for the interaction between Claw x Asym. The higher order interaction between Claw x Forehind x Time was significant, which is probably due to the asymmetrical loading of the claws being different in time for the fore and hind limb (Figure 2).
|
shows for each moment the absolute forces exerted to the lateral and medial claws of the fore and hind limbs, averaged over the left and right limbs. In Figure 2, the vertical GRF applied to the lateral and medial claws is shown as a percentage of the total vertical GRF exerted to the entire foot. The force is more or less equally distributed between both claws at the forelimbs during the stance phase. The distribution of the force at the hind limbs was remarkably different. At heel strike the load (± 1000 N 
1/6th of the BW) was almost completely exerted to the lateral claw. Subsequently, the force distribution equalizes gradually, so that at push off the applied load to lateral and medial claws was about the same.
|
|
). The contact area was significantly influenced by the factors Side and Time. The changes in contact area over time were different for the fore and hind limbs. At heel strike and at midstance the contact area was significantly larger at the fore limb, whereas at maximum deceleration, at maximum propulsion and at push off the contact area was not significantly different between fore and hind limb. The first-order interaction between Fore-hind and Time was statistically significant (Table 1). The asymmetry changed also over time, so there was a significant interaction between the factor Asym and Time.
|
). However, at push off the average pressure increased to 80 to 85 N/cm2 at both limbs. This effect was statistically significant (Table 1, factor Time). Also, the factors Asym and Fore-hind showed significant effects. The average pressure was significantly higher at the fore limbs at moment 2, 3, and 4. Furthermore, there were no significant interactions.
|
it can be seen that at heel strike the maximum pressure was about 88 N/cm2 at the hind limbs and 107 N/cm2 at the fore limbs; the maximum pressures were higher (± 105 and ± 130 N/cm2, respectively) the next three moments for both the fore and hind limbs. At push off, the maximum pressure increased up to 180 and 200 N/cm2. The maximum pressure was significantly influenced by all factors (Table 1). No interactions were present. At the first four moments the maximum pressures were significantly higher at the fore limbs, whereas at push off both limbs were subjected to the same maximum pressure. |
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
|---|
The forces applied to the force/pressure measuring system are measured simultaneously. The Footscan Pressure plate uses the output (vertical GRF) of the Kistler Force plate to equalize the summation of the forces applied to all individual sensors of the pressure plate to the total vertical force determined by the Kistler force plate. The pressures exerted to this force- and pressure-measuring system are determined more accurately than in stand-alone pressure plates/mats. Due to the relatively long surface of the measuring system (± 1 m) and the long acquisition time, the number of trials necessary to obtain five good measurements for all feet was rather low (about 40 walks per cow).
Distl et al. (1990) and Mair et al. (1988) quantified the pressures underneath the fore limbs of standing cows at a sampling frequency of 1 Hz. However, their low sampling frequency did not allow investigation of walking cows. Their results were partly in line with the results of van der Tol et al. (2002). Scott (1988) determined once the instantaneous weight bearing area at midstance during walking with the aid of a pressure-sensitive optical system. This method does not enable quantification of the pressures at the weight-bearing area. The present experiment shows that the pressure distribution at walk strongly depends on time. Therefore, only a method employing a high sampling frequency as well as a high spatial resolution will be suitable to analyze the pressures during locomotion.
A representative sample of Dutch high-producing dairy cows was conducted to the experiment, which took place at the end of the grazing period, and 2 wk after trimming their hind feet. Therefore, their claws were considered to be in good condition. In general the five measurements taken per limb were consistent and consequently the average of these five measurements was considered representative for the animal. No strict selection for age, weight, state of lactation, and/or clinical conditions had been applied. However, judging the level of the standard deviations, the results obtained from this heterogeneous sample can be considered as uniform and, as far as could be determined, consistent with previous studies (Toussaint-Raven, 1973; Ossent et al., 1987; Mair et al., 1988; Distl et al., 1990). A rubber floor was provided in this experiment to allow normal locomotion. The results obtained, therefore, provide a standard for loading conditions at normal locomotion of dairy cows with healthy claws.
Spatial Data
This study is the first to describe the in vivo force distribution between the claws of walking cows. At the five moments of interest the force was distributed more or less equally over the lateral and medial claw at the forelimbs. However, the force distribution at the hind limbs was remarkably unbalanced; at the first four moments a significantly greater part of the vertical GRF was exerted to the lateral claw. The data obtained by Toussaint-Raven (1973) and Ossent et al. (1987) have shown that the claws take uneven loads while standing. This effect appears to be even greater in walking. As the forces exerted to the limbs during walking are higher than during standing, the claws would be more prone to injuries, due to the uneven loading, particularly in the hind limbs. Uneven wear of the two claws is promoted by this loading pattern (Murphy and Hannan, 1987).
The maximum contact areas during walking were about 54 cm2 at the forelimbs and 47 cm2 at the hind limbs. A pilot study of Nilsson et al. (2002) showed contact areas in a range from 52.5 to 67.5 cm2 of cadaver claws mounted in a press and in vivo measurements on one walking (Holstein-Friesian) cow. Although no explanation was given for the discrepancy, the limited tendon support and the direction of force used in the in vitro study, the trimming method used (or not used), and the amount of time after trimming when the in vivo measurements were performed (1 mo) are probably reasons for the discrepancy in contact areas between these studies.
Horn: Mechanical Loading and Strength
The cyclic compression of claw horn during standing and walking constitutes a risk for fracture, which, in turn, may play a role in the development of claw disorders and lameness. To assess the risk, the in vivo pressures must be related to the compressive strength of horn. Baggot et al. (1988) determined the shore D hardness (SD) of horn samples of the wall, central sole, and bulb area of the hind claws for normal and lame cows. At all sample sites the lame cows had significantly softer horn. In normal cows, the bulb area consists of the softest horn (SD = 31.0), the sole area was harder (SD = 43.7), and the wall samples (SD = 65.5) were hardest. The hardness of the horn at several sample sites in the wall at 2-yr-old was even higher 70 to 75 SD (Russke, 2001). The modulus of elasticity (E), a measure of stiffness, of horn samples taken at the dorsal wall, abaxial wall and sole of the claws of all limbs were significantly higher at the forelimbs. Horn at the sole was four to five times more elastic than wall horn (Zöscher, 2000). Horn at the sole of hind limbs (E = 106.4 N/mm2) was significantly softer than at the forelimbs (E = 162.3 N/mm2).
Horn hardness and elasticity correlate roughly with strength, wear resistance, and brittleness. However, these hardness data should be used prudently, as they depend on the chemical composition and humidity of the keratin (Baggot et al., 1988), which is influenced by the condition of the animal, environmental humidity (housing) and the use of formaldehyde footbaths. For risk assessment it would be interesting to express the in vivo pressures as a percentage of the ultimate compressive strength. Webb et al. (1984) determined the ultimate compressive strength of the wall of the claws of pigs at 800 N/cm2. In cows, the compressibility of bulb horn is four times higher than of wall horn (Zöscher, 2000). If the difference between the compressibility of wall and sole horn is indicative for the compressive strength, the compressive strength of bulb horn would be four times less than the wall horn, i.e., 200 N/cm2. Consequently, the maximum pressures measured on the bulb of the lateral hind claw while walking (100 to 125 N/cm2) constitutes a significant repetitive load. Faster locomotion and sudden movements may result in an increase of the GRF per limb; uneven or partial support of the claw (e.g., grooved and slatted floors) may decrease the bearing area and increase pressure. In both cases pressures may increase to or beyond ultimate values and produce fractures of the horn or haematoma at the corium. It should also be taken into account that compressive strength of horn may be reduced by environmental humidity (wet floor) and adverse health conditions.
|
CONCLUSIONS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
|---|
The present study revealed that in normal cows the force and pressure distribution at walk on a hard surface form a potential risk for claw integrity, for the following reasons. First, in the hind limb the lateral and medial claws are loaded unevenly during most of the stance phase, which may lead to uneven wear and/or growth of horn. Second, during normal locomotion with healthy claws on a flat surface covered with rubber, the pressures exerted to the contact area reach up to 50% of the probable ultimate strength of horn. This threatens particularly the weakest positions of the claw (the bulb) with mechanical failure. Consequently, a combination of faster, unsteady locomotion or partial claw support may easily lead to overloading and horn fracturing.
|
ACKNOWLEDGEMENTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
|---|
Received for publication December 11, 2002. Accepted for publication February 4, 2003.
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONSACKNOWLEDGEMENTSREFERENCES |
|---|
This article has been cited by other articles:
|
|
 |
|
  E. Telezhenko, C. Bergsten, M. Magnusson, M. Ventorp, and C. Nilsson Effect of Different Flooring Systems on Weight and Pressure Distribution on Claws of Dairy Cows J Dairy Sci, May 1, 2008; 91(5): 1874 - 1884. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Platz, F. Ahrens, J. Bendel, H. H. D. Meyer, and M. H. Erhard What Happens with Cow Behavior When Replacing Concrete Slatted Floor by Rubber Coating: A Case Study J Dairy Sci, March 1, 2008; 91(3): 999 - 1004. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. M. Dyer, N. K. Neerchal, U. Tasch, Y. Wu, P. Dyer, and P. G. Rajkondawar Objective Determination of Claw Pain and Its Relationship to Limb Locomotion Score in Dairy Cattle J Dairy Sci, October 1, 2007; 90(10): 4592 - 4602. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. V. Kremer, S. Nueske, A. M. Scholz, and M. Foerster Comparison of Claw Health and Milk Yield in Dairy Cows on Elastic or Concrete Flooring J Dairy Sci, October 1, 2007; 90(10): 4603 - 4611. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. W. Meyer, M. A. Weishaupt, and K. A. Nuss Gait Pattern of Heifers Before and After Claw Trimming: A High-Speed Cinematographic Study on a Treadmill J Dairy Sci, February 1, 2007; 90(2): 670 - 676. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. G. Rajkondawar, M. Liu, R. M. Dyer, N. K. Neerchal, U. Tasch, A. M. Lefcourt, B. Erez, and M. A. Varner Comparison of models to identify lame cows based on gait and lesion scores, and limb movement variables. J Dairy Sci, November 1, 2006; 89(11): 4267 - 4275. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. P. J. van der Tol, J. H. M. Metz, E. N. Noordhuizen-Stassen, W. Back, C. R. Braam, and W. A. Weijs Frictional Forces Required for Unrestrained Locomotion in Dairy Cattle J Dairy Sci, February 1, 2005; 88(2): 615 - 624. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. G. C. J. Somers, W. G. P. Schouten, K. Frankena, E. N. Noordhuizen-Stassen, and J. H. M. Metz Development of Claw Traits and Claw Lesions in Dairy Cows Kept on Different Floor Systems J Dairy Sci, January 1, 2005; 88(1): 110 - 120. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. J. Collis, L. E. Green, R. W. Blowey, A. J. Packington, and R. H. C. Bonser Testing White Line Strength in the Dairy Cow J Dairy Sci, September 1, 2004; 87(9): 2874 - 2880. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Ceballos, D. Sanderson, J. Rushen, and D. M. Weary Improving Stall Design: Use of 3-D Kinematics to Measure Space Use by Dairy Cows when Lying Down J Dairy Sci, July 1, 2004; 87(7): 2042 - 2050. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. P. J. van der Tol, S.S. van der Beek, J. H. M. Metz, E. N. Noordhuizen-Stassen, W. Back, C. R. Braam, and W. A. Weijs The Effect of Preventive Trimming on Weight Bearing and Force Balance on the Claws of Dairy Cattle J Dairy Sci, June 1, 2004; 87(6): 1732 - 1738. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
) and maximum pressure (Pmax: 
•) exerted to the fore and hind limbs at moments 1 to 5 during the stance phase. Each value represents an average of the left and right limbs.