Can I tell you a secret?…I find hooves absolutely fascinating.
Most people think of hooves as being like a fingernail, a tough outer covering that protects structures underneath. Hooves are even made of keratin, which is like fingernails, except the organization and growth of hoof horn is completely different. Hoof structure is very unique, but without the aid of some great diagrams and histologic slides, it’s hard to get a handle on exactly what’s occurring in the epidermal and subcutaneous layers. If you’re interested, try googling “hoof diagrams” and “hoof histology”—it’s true that pictures are often worth a thousand words. Fortunately, what I want to talk about is pretty superficial and fairly logical.
Most external epithelium undergoes keratinization, a process in which an epithelial cell loses its organelles and becomes filled with keratin fibers, to increase its durability. In the hoof, the keratinization we’re concerned with is performed by the coronary band, a region just below the fetlock, and which marks the beginning of the hoof itself. Coronary horn produced by the coronary band is very durable, and very proliferative, as it is meant to be worn down by continual movement of the animal. When animals aren’t walking over rough terrain or are housed indoors on padded floors, the horn isn’t worn down and actually overgrows.
Why do we care about overgrown hooves? In the case of very heavy animals like cows and horses, hooves need to provide a flat surface for even weight distribution, or else bruises and pressure sores can develop. In worst case scenarios, the wonky weight distribution can cause the bone encased in the hoof, the distal phalanx, to rotate and possibly even puncture the sole of the hoof. Maintaining a flat cow hoof can be difficult because, since cattle have cloven hooves, the outside hoof wall is usually much more worn than the inside hoof wall, again because of the weight distribution. This is why cattle should have their hooves professionally trimmed at least twice a year, to prevent lameness and the associated lowered meat and dairy production. In the case of sheep and goats, overgrown hoof horn commonly contributes to lameness through footrot, a condition that occurs when anaerobic bacteria from manure grow in the folds of overgrown hoof and start destroying the horn. This leads to malformed hooves and pain, which again result in lameness and a loss of production. Small ruminants should have their hooves trimmed every six weeks and more often if footrot is suspected.