In a previous column, we discussed the reasons for routine evaluation and trimming of a cow’s foot in order to properly maintain the weight-bearing surface of the hoof (claw). To better understand the importance of a balanced, weight-bearing surface, it is important to understand the basic anatomy of the foot.
To begin, let’s focus on the internal anatomical features of the foot (Figure 1). The foot of the cow contains the portion of the limb below the fetlock joint and would be similar to our fingers and toes.
A cow’s foot is comprised of two digits (toes) that are protected by the horn-covered claw capsule. Each of the digits contains four bones: phalanx 1 (P1; not shown in the figures), phalanx 2 (P2), phalanx 3 (P3), and the navicular bone (NB). All of these bones serve as support structures for the leg and the rest of the body. The remaining internal components of the foot include:
• Corium: nerve and blood supply to the horn-producing areas of the hoof.
• Digital cushion: tissues that function like an elastic shock absorber between P3 and the corium, and as a pump that transports blood back up the leg as the cow walks.
• Lamellae: strong fibers that attach the wall to P3.
Now let’s look at the components of the claw surface as it would be viewed during a claw examination and/or trim (Figure 2). The weight-bearing surface is shaded in red and consists of the heel bulb, wall and sole. Components of the claw surface include:
• Heel bulb: composed of soft, rubbery horn originating from the same horn found within the coronary band (shown in Figure 1).
• Wall: consists of very tough, tubular horn and is smooth and shiny; however, faint ridges can be found running parallel to the coronary band.
• Sole: ideally one inch thick at the tip of the toe, becoming thicker towards the bulb.
• White line: the softest horn within the claw, providing flexibility between the harder horn of the wall and the softer horn of the sole.
• Interdigital space: the skin and tissue separating the two claws.
It is important to remember that cattle stand “in” their feet and not “on” them. As you’ll note in Figure 1, P3 is suspended within the claw horn capsule by the laminar corium and collagen fiber bundles. This type of attachment ensures that the weight is transferred from P3 onto the hoof wall when the cow walks and the foot is placed on the walking surface.
Knowing the anatomical features of the foot and claw will help you better understand the foundation necessary for improving hoof health on the dairy. In the months ahead, we will be discussing functional trimming procedures, the identification of claw lesions and the factors that cause them. EL