In our previous article in this series, we talked about the economic impact of lameness. In order to reduce the incidence of lameness and its associated costs effectively, it is important to understand the causes behind lameness and foot problems. To explain properly, we need to know the forces and pressures that play a role when walking in light of the anatomy of the foot. In 99% of cases, the cause of lameness originates in the feet, and the majority are located in the lateral hind claw. But why?
When a cow is walking, one leg is swinging to the front (swing phase), while the three remaining limbs are in contact with the floor (stance phase). Two of the legs are firmly standing and one is propelling the body forward (pushing off). So, when walking, the weight on the limbs in firm contact with the floor is about twice as much as when standing still with all four feet on the ground. For a cow of 700 kg this means a peak weight of 400 kg on a front limb and 300 kg on a hind limb at some point during its stance phase.
The weight applied to the front limb is more or less equally distributed over both claws (Figure 1a). However, with the hind limbs a remarkable difference occurs: the lateral claws take a major part of the weight when walking. At heel strike, the moment when the foot lands, the total impact is exerted to the lateral claw and this impact is mainly distributed to the lateral claw (Figure 1b) and this continues for the remainder of the stance phase. Close to 80% of the weight put on the hind limb is taken by the lateral claw!Figure 1. The total vertical weight (◦) expressed in Newton per kg body weight and its distribution between the medial (+) and lateral (*) claw for a) front limbs and b) hind limbs during the stance phase. For a cow of 600 kg it means maximum force is about 5.5 N/kg x 600 kg = 3,300 N, which is about 330 kg at 65% of the stance phase.
It is known that lateral hind claws are more susceptible to infectious claw lesions such as digital dermatitis, white line cracks and sole ulcers. This can be explained by the anatomy of the claws. The bulb area of the claw consists of the softest horn, sole samples are harder and wall-samples are hardest (Figure 2). The keratin of the forelimbs is stronger than in the hind limbs. However, claws of lame cows are composed of even softer horn by virtue of a higher horn turnover, as the hoof tries to grow thicker soles in an attempt to cope with these high impacts and forces. Hence regular trimming is required.Figure 2. Anatomy of the claws.
Running, mounting or sudden movements may increase the weight applied to a single claw. Uneven or partial support of the claw (e.g. slatted concrete) may decrease the bearing surface. In both cases, forces may increase to or beyond ultimate values and fracture the horn. Once such a crack is present, bacteria can grow inside it. Manure might cover up the damage and these bacteria can do their devastating job and cause an infection.
In the meantime, as a farmer you can provide the best conditions for your cows. Horn hardness and elasticity are influenced by animal condition and chemical composition of the keratin. Therefore, a good balanced diet and sufficient trace elements (e.g. biotin) need to be provided as a basis. In addition, the infection pressure in the cows’ environment can be reduced by regular cleaning and disinfection of the claws with, for example, Lely Meteor. Despite a good diet and a clean environment, the effect of these is reduced when claw shape is neglected. Especially when overgrown lateral claws are present, farmers need to schedule preventive trimming on a regular basis. Lely T4C provides you with the option of alerting you in time and routing your cows for a check on their hooves by the claw trimmer. In conclusion, in order to tackle claw lameness, all three aspects should be addressed to be as effective as possible.
In the next issue we will show the current developments in alerting for lameness in cows.
Cow health, Milking
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