Lameness is one of the largest health problems on United States dairies, costing producers thousands of dollars annually in higher costs and culling rates, as well as reduced milk production. Another area sore feet negatively impacts is reproductive function, and research continues to show that lameness and breeding pen performance are closely related.
Lameness 101: Hoof anatomy
It’s nearly impossible to understand why the dairy cow’s hoof responds to stress in the ways it does without understanding its structure, which is illustrated in Figure 1.
As you’ll see from the illustration, the bones found in the hoof are suspended by thick layers of cartilage rather than connected directly to the hoof. Without hoof health problems, the bones will remain suspended within the cow’s foot. When problems arise the cartilage is not able to keep the bone suspended anymore, and the P3 bone in the cow’s foot presses down on the other bones. Foot ulcers are one of the most common results of this pressure.
What’s the cause of lameness?
What makes treating lameness so difficult is that there are many different causes of sore feet. Some of the most common reasons include:
- Standing surface. Confinement on concrete or other hard surfaces increases the effects of excessive load-bearing on cow’s feet. These physical effects are often further complicated because hard flooring surfaces tend to accelerate hoof growth, eventually overloading the claw and causing claw disorders. Confinement on hard surfaces alone can result in lameness; factor in other challenges—including nutrition and environment—and the effects on lameness can be seen more quickly.
- Rumen acidosis. Although few studies established a direct link between rumen acidosis and laminitis, most assume that the feeding program is a major underlying factor. Acidosis is caused by
- varying degrees of rumenitis which encourages the absorption of lactate, endotoxins and bioactive messengers. These, along with many other substances like epinephrine and norepinephrine, cytokines and prostaglandins, are believed to have direct effects on the vascular endothelium of the corium in the hoof.1
- Calving. Hormonal changes during the transition period have more recently been linked to lameness. Relaxin is a hormone that relaxes the birthing canal before calving. When released it relaxes all of the connective tissue in the cow’s body, including that found in the cow’s hoof. This can cause the P3 bone to sink in the foot, which may explain why the incidence of lameness increases significantly around the time of calving.
- Enzymes. Hoofase is an enzyme that has been identified in pregnant heifers near calving. This enzyme activates other enzymes and processes known to weaken the suspensory apparatus of the hoof bones in first-calf heifers.
- Change in body condition. Cows have a digital cushion in the bottom of each foot that consists of saturated fat in heifers and unsaturated fat in cows. Research shows the size of the cushion and the fat composition is linked to body condition score (BCS). As BCS declines, so does the size and type of fat in the cushion because the body mobilizes this fat source for other maintenance requirements.
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