The pressure distribution under the bovine claw while walking was measured to test the hypotheses that the vertical ground reaction force is unevenly distributed and makes some (regions of the) claws more prone to injuries due to overloading than others. Each limb of nine recently trimmed Holstein Friesian cows was measured five times while walking over a Footscan pressure plate firmly embedded on a Kistler force plate. The pressure plate had a spatial resolution of 2.6 sensors/cm2 and was sampled simultaneously with the force plate with a temporal resolution of 250 measurements/s. Five moments during the stance phase were selected on basis of the force plate recording for the analysis of the pressure distribution: heel strike, maximum braking, midstance, maximum propulsion, and push off. At the forelimbs, the vertical ground reaction force was equally distributed between medial and lateral claw. At the hind limbs at heel strike, the force was exerted almost completely to the lateral claw. During the rest of the stance phase the load shifted towards the medial claw, until, at push off, it was more or less equally divided between both claws. The average pressures determined were 50 to 80 N/cm2. Maximum pressures increased from 90 to 110 N/cm2 at heel strike to 180 to 200 N/cm2 at push off. It was concluded that at the hind limb these pressures constitute a major threat to overloading particularly for the softer parts of the lateral claw, e.g., the sole and bulb area.

Claw disorders and lameness in dairy cattle are an increasing problem of the modern dairy industry. To prevent claw disorders from evolving from the subclinical to the clinical stage, trimming is the management practice most routinely applied. The goal of preventive trimming (Toussaint-Raven method) is to promote natural loading by increasing the weight-bearing contact area of the claws and improving the balance between the medial and lateral claw. The biomechanical effect of preventive claw trimming was investigated with the aid of pressure distribution and ground reaction force recordings of the standing cow sampled simultaneously at 250 Hz. It appeared that preventive trimming of the hind limbs (n = 10) brought the claws slightly more in balance. Before trimming, 80% of the total force is taken up by the lateral claw and 20% by the medial claw. After trimming, this becomes 70 to 30%, respectively. Thereby, a significant increase in the weight-bearing contact area from 27.5 to 40.0 cm2 was achieved, resulting in a significant decrease in average pressure. However, the claws remained subjected to unaltered, high maximum pressures after trimming. The suggestion was made that the main focus of claw trimming should not be force balance; instead, a reduction of local maximum pressures at the contact area should be targeted in such a way that the strongest parts of the claw capsule (i.e., the wall) will be subjected to the highest pressures.

The distribution pattern of pressure over the bovine claw was investigated to test the hypothesis that the ground reaction force is unevenly distributed and makes some regions of the claw more prone to overloading and injury than others. In eight recently trimmed Holstein Friesian cows, the distribution of vertical pressure was measured during square standing with a spatial resolution of 2.6 sensors/cm2 and a temporal resolution of 313 measurements/s. In each animal, the localization of maximum pressure per foot and per claw was determined during five trials. In the front limb, maximum pressures were normally found on the medial claw; in the hindlimb they were located on the lateral claw. In both claws, the highest pressures were found on the sole of the foot and not on the wall. In the front limbs, maximum pressures were located in the posterior portion of the sole; in the hind limb in the anterior portion. There was no difference in the location of the maximum pressure between the medial and lateral claw in either limb. The regions in which these maximum pressures occur are known to be relatively susceptible to injuries. This could indicate a causal relation between the location of pressure concentrations and claw diseases found in clinical observations.

Most free-stall housing systems in the Netherlands are equipped with slatted or solid concrete floors with manure scrapers. A slipping incident occurs when the required coefficient of friction (RCOF) exceeds the coefficient of friction (COF) at the claw-floor interface. An experiment was conducted to measure ground reaction forces (GRF) of dairy cows (n = 9) performing various locomotory behaviors on a nonslippery rubber-covered concrete floor. The RCOF was determined as the ratio of the horizontal and vertical components of the GRF. It was shown that during straight walking and walking-a-curve, the RCOF reached values up to the COF, whereas for sudden stop-and-start responses, the RCOF reached values beyond the maximum COF that concrete floors can provide. Our results indicate that concrete floors do not provide enough friction to allow natural locomotory behavior and suggest that tractional properties of floors should be main design criteria in the development of better flooring surfaces for cattle.

Metals in agricultural structures are often subjected to adverse environmental conditions resulting in high corrosion rates (up to 200 m/yr). The di!erent factors enhancing metal corrosion in farm buildings include high humidity and temperature, high concentrations of aggressive gases, acids, and salts (from silage and feed residues, cleaning agents, manure, fertilizers, preservatives), mechanical destruction and bacteria causing microbially induced corrosion. The importance of microbially induced corrosion is not yet clari"ed and a reduction in corrosion by bio"lms on metals has also been reported. Corrosion products found in animal houses are similar to those resulting from classic corrosion mechanisms, which may lead to the conclusion that the fundamental mechanisms of metal corrosion in animal buildings are similar to the classic ones. Di!erent methods to detect, measure and predict corrosion are described. The economic losses by corrosion in agriculture are evaluated. By corrosion prevention, a reasonable amount of expense can be saved. Prevention includes: (1) the choice of corrosion resistant materials such as stainless steel or non-metallic materials; (2) designing against corrosion; (3) control of the aggressive environment; and (4) application of coatings. When protective coatings are used, such as zinc layers and painting systems, surface preparation of the metal is of the utmost importance. Zinc layers should be thick enough ( '50 m), and zinc-coated steel should be protected in areas of extreme aggressiveness, such as "ttings at #oor level. Reports about the durability of di!erent painting systems in agricultural structures are reviewed. The development of new environmentally friendly products is discussed. Guidelines for maintenance of previously painted steelwork are formulated. Silsoe Research Institute