Foot and Claw Physiology

While knowledge of the factors that affect cow hoof health is important, understanding the structure of the foot itself, how the various parts of the foot's physiology interact with one another and how each part can be affected or damaged by routine activities on the farm will help to underline the importance of good hoof health and how easily mobility problems can occur. It will also be of use when formulating treatments or performing foot trimming.

A cow's weight is distributed between all four feet, with the front hooves usually bearing in the region of 50-60% of the weight, although in younger cows, heifers and calves, that figure is more likely to be nearer 50%. When the cow is standing squarely and the claws are of even height and stability, the part of the body-weight borne by either pair of legs should be evenly distributed. Abnormal wear can be caused where extra pressure is placed on one or more of the feet due to altered weight-bearing where one or more claws are injured or diseased. Ideally, the hoof angle should be around 45-50 degrees, and the claws should be slightly spaced.

The hoof grows very similarly to the human finger or toe nail. Several factors affect the growth of the horn, such as diet, body condition, genetics, housing or grazing conditions, general wear and weight-bearing forces. This is evident in the rings that often occur on a cow's hooves, where due to variations in these factors, the horn is produced at different rates. Illness and disease in addition to environmental hazards can contribute to uneven horn growth or overloading of the claws and weight bearing on the heel area. Lameness indicates a problemthat has deteriorated to the point where pain is felt and the cow consequently alters her gait or stance to cope.

The outer claw on the hind feet is usually slightly larger than the inner claw due to it carrying more weight and the action of the leg circumventing the udder during walking.The front feet tend to be used for controlling side-to-side movement, and so the inner claw is usually larger than the outer claw.

Ligaments and muscular tissues within the foot and lower legs also have a significant role in mobility, particularly during calving. Hormonal changes during the transition period, where hormones that relax the birthing canal are released can also systemically affect all of the connective tissues in the cow's body, including those found in the cow's hoof. This can cause an increase in mobility problems around the time of calving and has been recognised as a high risk time for cows and heifers.