The bovine hoof is an amazing thing. Two small bones at the end of each leg — the equivalent of the very last joint of our fingertips — are responsible for carrying a 450kg+ animal thousands of kilometres over her lifetime, much of this over gravel and concrete surfaces.
This bone is encased in hard horn (the outside of the hoof — similar to our fingernails), and rests upon a cushioning fat pad. It makes sense that we need to protect this small bone known as the 'pedal bone' as much as possible to ensure a long and productive lifetime.
When a cow becomes lame, this is often because of historic trauma to the foot.
Hoof horn grows out at a rate of 5mm per month. If the horn is damaged at the point where it starts growing from (where the hair of the leg and the hoof meet, and at the sole of the hoof), it may be as long as six months until this defective horn is at the business end of the foot where it is responsible for protecting the cow during her many kilometres walking to and from the shed.
Weakened horn is more likely to allow stones to track up inside the foot, which is often seen as white line disease.
A cow's natural reaction to white line disease and other injuries such as bruising is not always helpful. In an attempt to protect the area that is painful, the horn will thicken around the injury.
However, this puts pressure on the internal structures of the hoof which causes more defective horn to be made, and more seriously, can cause the pedal bone to grow sharp spikes of bone in response.
Once these bone changes occur, they are permanent, and will put the cow at a greater risk of lameness for the rest of her life.
The highest risk groups of animals for having damage to this important pedal bone are heifers and skinnier animals.
This is because they have less of a fat pad — the cushioning pad that sits between the pedal bone and the sole of the foot.
This pad acts like a shock absorber for the pedal bone. Even a mildly lame heifer may have bony changes occurring that will impact her for the rest of her lifetime, so it is critical to protect these animals.
To reduce the long-term effects of lameness ensure your animals (especially heifers) are in good condition and don't lose too much weight post-calving, so the shock absorbing fat pad can do its job.
Treat any lame cow as quickly as possible, by lifting the foot and removing excess horn around the injury site. If you are not confident doing this, have your vet in to look at her.
Putting a slip on the good claw to relieve pressure on the injured claw, and using NSAIDs (anti-inflammatory and pain-relief), have both been shown to be effective in reducing the damage to the pedal bone.
Remember that preventing and properly treating heifers now is an investment in their future in the herd.