Several things can cause foot soreness in cattle, including foot rot, puncture wounds, sole bruises, abscesses and white line disease. But one of the most serious is infection of the inner parts of the foot, resulting from toe-tip necrosis.
Dr. Murray Jelinski of the Western College of Veterinary Medicine at the University of Saskatchewan started looking at this disease 10 years ago. His brother, Dr. Mike Jelinski, is a feedlot veterinarian in Alberta, and the two got talking about feedlot diseases, including some that hadn’t been studied. Dr. Eugene Janzen at the University of Calgary and Dr. Oliver Schunicht of Feedlot Health Management Services were also interested in toe-tip necrosis. Schunicht had presented on the disease to the Western Canadian Association of Practitioners after investigating an outbreak in feedlot cattle.
“Back then people were not as aware of it, and it also had different names. In southern Alberta and the U.S. people were calling it toe abscesses,” says Jelinski.
The dairy sector sees white line disease, which sometimes leads to abscesses and develops more in the side wall of the claws.
“Toe-tip necrosis starts at the tip of the toe. Although the two diseases have some features in common, location suggests that causes may be different,” says Jelinski.
Jelinski and his brother asked feedlot practitioners in Alberta to submit feet from animals that developed toe-tip necrosis and were overwhelmed with the response; the disease was much more prevalent than they realized.
“Now there seems to be more cases, but this is what often happens — once you start looking for something you start finding more. Prevalence of toe-tip necrosis in the past 10 years may not have increased but our awareness has, leading to increased reporting,” he says.
Typically these cattle come off pasture, go into the feedlot and within a few days to a month develop hind limb lameness, says Jelinski. The disease usually starts in the lateral claw on a hind foot, and is rarely seen in the front foot.
“If you look closely, you see wear at the tip of the toe, and separation along the white line,” says Jelinski. “Depending on when you catch it, you might see the start of an abscess or just some separation.”
In bad cases the infection has already penetrated the hoof wall, going up into P3 (the coffin bone) in that claw. It can then travel through the tendons and into the bloodstream, he explains. Those cattle become septicemic, as pathogens travel to all organs and seed into the lungs.
“What we see is a classic embolic pneumonia, which we usually associate with liver abscesses. People rarely check the feet to see if there’s a foot infection to explain the pneumonia,” he says.
Several risk factors are associated with toe-tip necrosis. “A pathologist in South Dakota described outbreaks in feedlots in the U.S. in the 1980s. He found cases in clusters, in groups of cattle coming in. He wondered if there might be a temperament factor,” says Jelinski.
Dr. Karen Schwartzkopf-Genswein at the Lethbridge Research Centre, Janzen and Jelinski collectively investigated several outbreaks.
“It became clear that high-strung animals are more likely to get this disease,” says Jelinski. Flighty animals are more apt to injure the hind feet as they push forward in the chute or scramble on rough concrete surfaces.
“Cattle have so much muscle and strength in the hind legs that they put tremendous forces on their toes. If they slip and lose their purchase on the concrete, it is like a rasp and scrapes the toe off,” he says.
Toe-tip necrosis isn’t heard of much in cow-calf operations with pastured cattle.
“Even if cattle travel along a gravel road and stone bruise, that would be different,” says Jelinski. Jelinski and his colleagues think the damage occurs when cattle are being loaded or unloaded on trucks, or at the auction yard, as there is lots of concrete in areas where they are sorted.
“Some cases develop within 24 hours of arrival at the feed yard. That tells me the trauma is happening before arrival — perhaps in transit or at the auctions. We rarely see it later in the feeding period, so it is a disease associated with handling, perhaps on arrival. We have created it by management and can probably manage our way out of it.”
“When people have larger herds on bigger pastures or rangeland, cattle may not have been handled much. If they are only checked occasionally by people on quads or horses, cattle raised are more likely to be flighty,” he says.
Animals that die with toe-tip necrosis have a thinner white line than animals that die of all other causes, says Jelinski. The white line is usually about four to five millimetres in depth, he explains, so if they suddenly wear off a couple of millimeters, fissures develop in the foot. Bacteria then enter the soft while line and produce enzymes that break it down even more.
Jelinski has sectioned more than 300 feet over the years with a band saw. Sometimes he finds organic matter such as manure or straw that’s been impacted into the foot, he says. As the animal takes a step and loads the foot, the white line gapes open. When the foot is lifted it closes up again on any material jammed in there. Pathogens that thrive in a low-oxygen environment get impacted inside the foot and start an abscess, and infection may extend to P3 and surrounding tissues.
Researchers are currently studying flooring and footing at feedlots and auction marts, as well as on trucks and trailers.
“Cattle coming into a feedlot after a wet summer seem more prone to this disease; their feet are softer, more vulnerable to wearing away on abrasive surfaces,” says Jelinski.
He and his colleagues also looked at nutrition and micronutrients within the hoof wall and sole. Prairie Diagnostic Services conducted the analytical work for the project.
“We determined that magnesium levels in horn tissue — hoof wall and sole — were lower in cattle with toe-tip necrosis than in the controls,” he says. “Calcium is implicated in the integrity of horn tissue, but magnesium and calcium are interrelated, and if one is low, the other is low. I suspect that low magnesium could be an indicator for low calcium.”
There may be a nutritional basis to this problem, but trauma to the foot is the biggest factor. Thus prevention centres on flooring. Some feedlots have rebar welded together in a cross pattern, or rough concrete at their chutes. Cattle need adequate traction so they don’t slip and fall when leaving the chute, but not so abrasive that it damages the feet.
Cattle handling is also important. Fractious cattle must be handled quietly so they aren’t trying to flee or shove in the chute.
“We’ve seen outbreaks where 40 to 50 per cent of the cattle end up with toe-tip necrosis. In other instances it’s just an odd animal here and there,” says Jelinski. “I don’t think they are always fractious. Most diseases are the result of multiple factors that come together at the right time to tip over the animal’s defenses and develop the disease.”
More people are becoming aware of the risks. Animals developing hind limb lameness soon after entering the feedlot should be thoroughly checked.
“If there’s no other obvious cause of lameness, toe-tip necrosis is a possibility. To diagnose it we use hoof nippers to nip the end of the toe. You’ll either see a purulent bloody black-brown discharge, or a black crusty necrosis of horn tissue,” says Jelinski.
“In a current study we’re looking at best practices for treatment. Should we be nipping these toes, treating them like an abscess — to allow drainage — and give antibiotic coverage as well? Or is just nipping enough? Or just antibiotics?”
For treatment of toe-tip necrosis, long-acting antibiotics are generally successful if it’s caught early. However, often there’s separation of the white line before anyone realizes there’s a problem. If the infection gets to the corium (the soft inner tissue beneath the horn), it reaches nerves and blood supply.
“At that point it becomes painful and the animal is lame. If you treat it early, there is good blood supply there, so the antimicrobial would be in high concentration and treatment would be successful,” says Jelinski.
But once the infection reaches the coffin bone or P3, it’s more difficult to treat.
“We have sectioned feet from animals that recovered, and see that the bone has remodeled. If you treat aggressively enough, they can recover from a minor P3 infection, but once it gets advanced we are probably looking at amputating that toe.”
But it’s not unusual to find toe-tip necrosis in more than one of the hind claws, says Jelinski.
“If veterinarians are going to amputate a toe, they’d better check the other toes as well. Euthanasia may be the best option on some animals because this is a very painful condition. You don’t want to leave them three-legged lame in a pen with little hope for recovery.”