Lameness issues go beyond nutrition. Factors such as stockmanship, like crowding cows – by dogs or employees – in the open or in alleyways can also negatively impact foot health.
Editor's note: second in a two-part series on lameness.
When investigating causes of lameness on the dairy, it's important to understand the biomechanics and weight-bearing nature of the cow's skeleton and feet. "We know that 90 percent of lameness is the foot, 90 percent of that is in the rear feet and 70-90 percent is in the outside claw," explains Jan Shearer, DVM, MS, University of Florida.
You can gain a better sense of why this occurs in the rear, outside claw when observing the anatomy of the rear foot. The outside claw is larger, with a much flatter weight-bearing surface as compared to the inside claw, which is smaller and has a more sloped weight-bearing surface. "Based on Toussant Raven's work, the consequence is that when the cow puts her foot down, weight naturally rolls over to the larger, more naturally stable outside claw, instead of the less-stable and more sloped weight-bearing surface of the inside claw," says Shearer. "This has helped me get a much better understanding of why this pattern of lameness occurs in cattle – it has to do with weight-bearing."
As a result, the cow is naturally going to put more weight on the outside claw when standing on soft surfaces and hard, abnormal surfaces, such as concrete. "The combination of the two becomes very important in the context of lameness because both of those situations working together create problems for the cow," Shearer adds.
Another factor is how weight shifts through the cow's pelvis. The cow's pelvis is like ours – a fairly rigid skeletal structure with a ball and socket joint. As a consequence, when a cow leans one way or another, she ends up distributing weight to the side she leans to but not in an even fashion between the two claws – more of it goes to the outside claw. "The same thing happens when we stand and lean one way or another," says Shearer. "Weight is not distributed evenly. The inside claw stays relatively stable, but the outside claws are ever-adjusting for the extremes of weight-bearing."
Heel ulcer on the outside claw with a block on the inside claw to relieve weight-bearing on the diseased claw.
Photo credit: Jan Shearer, DVM
When a cow is on a pasture or soft surfaces, these effects of load-bearing are greatly diminished. When a cow is on a concrete surface, all of those effects are amplified because this cow is on a hard surface instead of a surface that absorbs the weight-bearing forces, and those forces are instead redirected back into the cow's foot. "Back in the cow's foot, it affects the corium or dermis of the claw," notes Shearer. "It's the same as in humans. When we stand on a hard surface, our feet begin to hurt, then our legs, then our back. A cow experiences the same kind of thing."
The sole and the whole claw capsule is modified skin but does not produce callouses like humans do. Instead, when the corium that forms the sole of the outside claw is irritated, the cow produces hoof horn. This eventually leads to overloading of the outside claw, and that ultimately gets corrected for by the cow cow-hocking herself. "When she cow-hocks, she pulls her hocks in and rotates her feet out so she can put more weight on the inside claw," explains Shearer. "That tends to help for a while, but there comes a point where no matter how much she cow-hocks herself or what she tries to do differently in terms of posture, the weight-bearing is always going to be unbalanced and will be greater on the outside claw."
When a cow begins to cow-hock herself, she pulls her hocks in and tries to rotate her feet out so she can put more weight on the inside claw and relieve the overloaded outside claw.
Foot shape and trimming
A study by Clarkson, et al, published in the Veterinary Record June 1996, found that cows with long toes or high heels were more likely to have lameness. "That makes sense because overgrowth in claws is a consequence of weight-bearing and hard surfaces," says Shearer. "These are cows that just needed hoof trimming primarily and developed lesions in their claws and feet as a consequence of the abnormal weight-bearing that comes with that."
Much like veterinary medicine, good hoof trimming involves a certain amount of art and science if it's done well. "There's an awful lot of dairy farmers who believe the concept of hoof trimming or claw trimming is a procedure that nearly anyone can do," says Shearer. "That's not true. What I've learned about claw trimming is that it is probably one of the more complicated things to do right. We're working with tolerances that are in the range of millimeters, not inches, when we're talking about a claw horn sole being a quarter of an inch."
Shearer believes that the best reason for trimming feet is based on Toussant Raven's system from the Netherlands, which is designed to balance weight-bearing between the two claws to make the cow's foot more functional. "It's simply a system that removes the excess toe length, balances the weight-bearing within and between the two claws to make the cow more functional, and reduces the excessive weight-bearing on one claw."
Traditional trimming approaches are designed to place the majority of body weight on the wall. The Toussant Raven system is designed to place weight-bearing not only on the wall but on the sole and on the heel. "Most of the people trimming horses" feet were the ones who trained all of us to trim cattle feet, and those were methods devised by farriers for horses," Shearer says. "We were taught to put the weight on the wall, which is where it needs to be for the horse but not the cow."
Understanding the difference in hoof anatomy between a horse and a cow makes those older methods obsolete. In the horse, there's a much larger region of laminar corium, which is the suspensory apparatus of the hoof. The horse also has a secondary set of laminae that creates a tremendous surface-area for weight-bearing on the wall, but this secondary set of laminae does not occur in the cow's claws. So, Shearer says, the Toussant Raven system for placing weight on the sole, wall and heel makes more sense for cows.
Claw trimming is a useful management procedure and can prevent lameness. A good trimmer can do a lot to reduce the incidence and problems in herds. A poor trimmer can do a lot to increase the incidence of lameness in herds. "It always surprises me that dairy farmers will risk $100,000 of their investment to a trimmer they may not know anything about and put that many animals at risk," says Shearer.
Housing and cow comfort
When a lot of dairy farms have lameness issues, they tend to focus on nutrition and feeding errors. "Those are important causes of lameness in some herds, but I think that people underemphasize the significance of housing and lameness," says Shearer.
But factors such as cow comfort, housing, standing on concrete, stockmanship issues and others serve to exacerbate lesions once they occur. "Cow comfort, including stall design and bedding, combined with concrete, is the most important cause of lameness in California," says Dale Moore, DVM, MPVM, PhD, University of California.
"In a nutshell, there are more expanding herds, larger herds and better performance than we've ever had, and we've got more confinement housing – and more concrete – as a natural consequence of larger herds," says Shearer.
Clarkson's survey of dairy farms in England and Wales showed that housing was one of the factors associated with a higher incidence of lameness. There was more lameness in the free-stall operations than in the cases where herds were housed in a pasture or straw-yard situation. "That is a very interesting factor that helps us understand, especially when we combine it with weight-bearing dynamics in cows, what is probably going on with housing and hard surfaces," says Shearer.
Not only is concrete less comfortable to stand on, hard surfaces create problems for the cow's foot in that it encourages claw horn overgrowth. "That can ultimately lead to problems with inappropriate weight-bearing between claws or within claws, and that leads into ulcers and white line disease problems," says Shearer. "More often than not, excluding digital dermatitis, the primary causes of lameness in cattle are claw disorders associated with ulcers or white line disease."
"We know that lame cows struggle to use poorly designed stalls – rising and lying movements are very difficult when you have a sore foot," says Nigel Cook, BVSc, University of Wisconsin. This results in the cow standing in the stall during a stall-use session for prolonged periods of time "waiting to lie down," adds Cook. "This excessive standing, we believe, increases the duration of the lame event." Standing on concrete for prolonged periods waiting to be milked is a similar problem and represents time when the cow would rather be lying down. Walking too far on rough concrete also causes excessive wear.
Confinement housing also contributes to the constant exposure of cows" feet to manure slurry and moisture that can predispose them to infectious claw disorders, such as PDD, and can also encourage foot rot in some cases, as well as heel erosion.
Heat stress and lameness
Another issue of cow comfort and housing involves heat stress. Shearer says there's a seasonal pattern (late summer into the fall) to lameness problems on the University of Florida dairy. The incidence of lameness for 1994-95 (similar current incidence) was about 51 percent, with 35 percent of the cows affected. "At least, what we see would suggest that heat stress is part of the problem," says Shearer.
When a cow is heat stressed and open-mouth breathing, she loses moisture through increased respiratory rates and drooling. A large amount of saliva is lost that normally would go back into the rumen for buffering. Heat stress affects the acid-base balance and encourages rumen acidosis problems, despite proper feeding and feeding management. The increased respiratory rate causes respiratory alkalosis. Generalized alkalosis leads to a situation where the cow tries to compensate by increasing her urinary output of bicarbonate. The panting and the drooling losses plus the loss of bicarbonate in the urine actually put her in the position of being base-deficient.
"We end up with more rumen acidosis as a consequence of heat stress for cows in the summertime," notes Shearer. "Even for shorter periods of hot weather, such as in the Midwest, it can be an issue as it is across the South for longer periods of time."
How cattle are handled can have a significant impact on lameness, as well as how they are housed.
Rushing cows may lead to hoof trauma, says Cook, "a notable problem in New Zealand dairies where cows are rushed along rough tracks."
To illustrate that, Shearer cites a study done by New Zealand veterinarian Neal Chesterton, who videotaped a single cow walking over a concrete pad where he had scattered rocks. As she walked across, she had her head down, watching where she placed her feet and didn't step on any of the rocks. Where the front foot came up is precisely where the back foot came down.
Then he brought the single cow back and ran her with a group of cows across the concrete pad, and in the process of moving them across, he moved them at his pace, more rapidly, and from the back of the group forward. "It caused a real problem because the cow in the front is still looking where she's placing her feet, but the cow in the back is trying to get away from the herdsman and, as a consequence, all the cows were walking on rocks," says Shearer.
Another example on large dairies is the use of a crowd-gate system. In some cases, they are electrified and set so the pressures are tight, so that when they come forward, cows try to get away. "In some cases, cows in the back are rolled over or hurt by the crowd gate and can have broken legs, stifle injuries from ligament damage, etc.," says Shearer.
Shearer would like to see more dairies keep track of the cows they lose from upper-leg injuries. "In some situations those numbers may be significant enough to warrant taking a closer look at cattle-herding methods, be it a crowd gate or other things."
"I have become far more sensitive to the welfare issues," says Shearer. When he sees a large number of animals in a lame cow lot on a dairy, one of the first things he does is assess how many of those cows actually have a treatable condition. If they can't be treated and they are able, they need to be moved onto slaughter or in many cases need to be euthanized if appropriate.
"It's not intentional, but sometimes dairymen or managers don't know enough about foot problems to understand when to say when," says Shearer. "That's where veterinarians have a very important role. We need to help them know when to say when on these animals, so they don't suffer. Some have no hope of getting better, and we need to recognize that and move on."
"The veterinarian is the best person to assess the prognosis for a cow," Moore agrees. "He or she can counsel the client on euthanasia or slaughter by ascertaining the demeanor, nature of the pain and mobility limitations of the lame cow."
Shearer emphasizes that when veterinarians train dairymen in foot care, it's important that they understand the conditions they can fix and those they can't. "Whether it's sell or euthanize, the economics of hanging onto that cow and hoping she'll get better is really short-sighted."
Moore is mulling over the idea of pulling cows early for trimming, before they become lame, by assessing their hind-limb posture. However, it would be an added expense. "I would like to see someone pursue this over a period of time and see if we can prevent clinical lameness and pain from occurring," she says.
Welfare also involves cattle handling and facilities. Shearer notes that many operations that have set up facilities for working cattle seem to have forgotten that they are working with cattle. "Feedlots, for example, have set their systems up so they can move animals with a minimum of prodding and so forth, which is also a welfare issue. I am disturbed to see hot shots used to get cattle moved. Setting these systems up in a way that cattle will naturally move through is really important. It bothers me that many dairymen have not taken more effort to set these facilities up appropriately for cattle movement."
One thing dairies with few lameness problems have in common is good cow comfort.
Dairies that do it right
So what are the dairies that have little lameness doing different than other dairies? Excellent herd health, nutrition and cow comfort can prevent lameness from occurring in the first place, says Dale Moore, DVM, MPVM, PhD.
One factor is knowledge, training and awareness by the dairyman about lameness. "The more of that they had tended to affects how much lameness they had, and that's what a lot of veterinarians see with their clients," says Jan Shearer, DVM, MS. "Clients who are concerned don't tend to have as much as some folks who haven't recognized the significance of this problem in their operation."
Shearer adds that dairies with fewer lameness problems have an emphasis on good feeding practices and nutritional management, but they also are very sensitive to good cow comfort. "They design their stalls and keep them bedded in such a way that encourages a cow to want to lie down. Those are critical issues right there." They have good heat-stress management, good foot-care programs and good people who are well-trained on-farm. "When they put enough time into those things, you see very good foot health on dairies."