Part 1: hoof anatomy and how lameness happens
by Sally Colby
Dr. Ernest Hovingh, extension veterinarian, Penn State University, echoes what dairy farmers already know: that lameness in dairy cattle is an important problem in the industry. In addition to affecting reproduction, milk production and overall health, lameness is a true animal welfare issue that must be addressed.
“Think of it as preventing lameness,” said Hovingh. “That’s where to start. But we will always have some lame cows, so we have to have a system in place to identify those cows, and be able to intervene and avoid associated costs. We also want to manage cows so they return to health and production in a timely manner, and use that information to prevent future lameness.”
What causes lameness? “Almost all lameness in cattle occurs in the feet,” said Hovingh. “Usually the outside claw of the hind feet. Some lameness occurs in the upper leg and pelvis, but that’s a relatively small percentage of all lamenesses, and not usually a herd or group problem.”
When Hovingh looks at herd lameness problems, he doesn’t usually see a single causative factor. “This is a complicated puzzle and a lot of factors interact,” he said. “While we can often find one factor that might be somewhat more important, we often have to address several aspects of herd health.”
Hovingh says that although nutrition, infectious claw disease and metabolic disorders contribute to lameness, the cow’s environment and herd management are the biggest factors. Just as individuals within a herd are different, lameness within a herd varies.
Both internal and external factors can contribute to lameness. “There are things that happen inside that foot that determine how healthy the foot is,” said Hovingh. “One is how strong and what condition the foot is in. Another part of the equation is the environment. Internal factors that contribute to a good hoof health include genetics along with proper nutrition with good ingredients so the cow can maintain a good structure to walk on.”
The cow lives in an environment that subjects the hoof to various external challenges — heat stress, walking surface, hygiene, foot bathing and trimming. “Cow comfort becomes very important in determining how the foot survives the environment,” said Hovingh. “Walking surfaces, how we ask the cow to walk across those surfaces and the way we handle cattle are important as well.”
Basic knowledge of hoof anatomy is important when it comes to understanding lameness. The corium, which is between the P3 bone and claw capsule, is the ‘worker’ tissue of the foot. It produces the hoof wall, claw, heel, sole, white line and the coronary band. The laminae is a specific section of the corium where there is a lot of blood flow to the area.
Laminitis is the condition of injury or inflammation in the laminae. The damage can happen anywhere in the corium. “When we refer to laminitis, we’re referring to damage or inflammation in any part of the corium,” said Hovingh. “When that happens, the corium makes poor quality sole tissue. It does its job, but it doesn’t do a good job. Or it might make poor quality heel tissue or white line tissue.” In some cases, the corium doesn’t make any tissue at all until the injury is healed.
One concern is that if the injury is severe enough, healthy tissue might grow back, but there’s still a defect in the hoof. So despite having a normal, healthy hoof, the cow might become lame in the future because her foot is potentially defective.
Cow weight, conformation of the foot and leg, and sole strength are important factors in lameness. Hovingh explains that when the sole is strong, the weight of the cow is distributed over a broader surface. Hoof shape and trimming technique can optimize the spread of pressure throughout the hoof.
The weight of the cow and how that weight is distributed on the bottom of the foot is a function of a structure on the bottom of the foot known as the fat pad (digital cushion). Hovingh compares the fat pad to a gel insert that might be used in a pair of shoes to absorb and spread the wearer’s weight. “There’s a significant space difference between the P3 bone and the corium down below the bone,” he said. “That’s similar to having a gel insert in your shoe. What happens is that when animals lose body condition, they tend to lose fat pads fairly quickly. There may be hormonal conditions that also contribute to the loss of the fat pad.” Hovingh referenced studies at Cornell University that showed when the fat pad is too thin, the chances of a sole ulcer or white line disease are higher. An insufficient fat pad can lead to a much greater chance for pinching the corium, so optimum body condition is important in keeping the fat pad healthy.
To understand lameness from the cow’s perspective, watch the way a cow walks and how the hoof hits the surface. “The cow doesn’t put the foot down completely flat,” said Hovingh. “The back of the outside claw tends to hit the walking surface first. That’s the normal walking pattern.”
Hoof shape contributes to weight bearing. Cows with untrimmed hooves will have unbalanced claws simply through natural growth, and some reactive growth from where the claw contacted the walking surface. Because the feet don’t wear evenly from front to back, cows end up with fairly long toes because the hoof wall protects the front of the sole.
“At the back, we end up with fairly thin soles,” said Hovingh. “That sole tissue is soft and wears off quickly because of the walking surfaces. We end up with long toes and a thin, shallow sole. What happens is that there is too much weight over the P3 bone and weight loading at the back. Good trimming can help distribute the weight more evenly over the P3 bone rather than have it concentrated on a small area at the back.”
Hovingh says a pastured cow with a good, concave hoof is usually going to fare well. “As she puts that foot put her foot down, the hoof wall will dig into the pasture, and then assuming that the pasture isn’t rock hard, the ground conforms to the bottom of her hoof and she’ll have weight transfer throughout the whole bottom of the hoof,” he said. “The weight transfer isn’t just through the hoof wall and the white line, it’s also through the bottom of the sole.”
Part 2 will focus on how cattle facilities contribute to lameness
Deconstructing lameness in dairy cows
Part 1: hoof anatomy and how lameness happens