health
the hooves that happens along the way from the farm to the feedlot. Typically, it starts in one or more hind claws, but can affect front claws as well. Jelinski says some feedlots see it more than others. The big risk factors seem to be transport time, animal temperament and floor conditions. Although most feedlots are aware of the condition, it is often misdiagnosed as an injury due to trauma or handling because lameness may start to appear within a few days after arrival. This is why treatment is often delayed. In the meantime, the infection may spread deeper into the claw tissues and bone where it becomes untreatable and ends up with the animal being euthanized. It’s often a surprise to see what’s going on in the hoof when the animal is necropsied, Jelinski adds. For more detail see our related story in this issue. Sloughing hooves
Constriction of blood vessels in the extremities due to frostbite and ergot poisoning may also cause lameness. Ergot toxicity has been more common in recent years with wet growing conditions more conducive to ergot bodies forming in cereal heads, says Jelinski. The severity of associated lameness problems tends to cluster by feedlot depending on where they source grain. Grain screenings in pelleted supplements are another source of ergot toxins. Ergot toxicity may first show up as lameness in the feet. Over time a line of demarcation (splitting of the skin) may become evident between the dead and healthy tissue. Some hooves may be affected worse than others and in severe cases the entire foot or claw sloughs off. “The degree of damage caused by ergot toxins depends on the amount of toxin consumed and animals may recover from low-level poisoning when contaminated grain is removed,” he says. Prairie Diagnostic Services at the Western College of Veterinary Medicine in Saskatoon now has equipment in place to test feed for ergot toxins. Laminitis
Laminitis is easy to recognize by the way cattle walk. They tend to throw their front feet forward and bring their back feet underneath trying to get their weight on the bulbs of the hooves. Some animals may kneel on their front legs in an attempt to take weight off their feet. www.canadiancattlemen.ca
In a healthy hoof, a layer of laminae cushioned between the hoof wall and the third bone (the bone coming down to the tip of the hoof) holds the bone parallel to the hoof wall. When laminae weaken or tear from the hoof wall, the third bone begins to rotate downward putting pressure on the sole. Laminitis in feedlot cattle is associated with a rapid increase in highly digestible carbohydrates (grain) in the diet, which changes the acidity in the rumen and in turn kills off some types of digestive organisms that release toxins into the bloodstream as they die. The toxins cause swelling in blood vessels of the hooves leading to impaired circulation. A hardship groove associated with an abrupt change in diet will become noticeable across the hooves as they grow out. Sole overgrowth, skinny claws (flipper feet) and other claw abnormalities may become apparent in time. Once laminitis sets in there is no practical treatment, however, animals with mild cases may get along just fine on soft ground in well-bedded pens. Marketing affected animals in a timely manner is advisable.
Fo ot rot Ex a mples
Bad Feet Foot rot
ergot in feet
Others
It can be very difficult to distinguish lameness when an infection is caused by injuries, according to Jelinski. Bruises, sprains, torn ligaments, ruptured tendons and, the very odd time, fractures can happen during routine handling and in pens when animals jostle at the feed bunk. Nerve and brain damage also cause peculiar behaviour and strange gaits which can be mistaken as lameness. Spastic paresis is an example of a hereditable condition where sensors in the muscle bundles keep the leg muscle tight causing the hock to hyperextend with each step. A severe joint infection can trigger an acquired form. Abscesses from needle injection sites too close to the spine have been known to create a “wobbler” when the infection pushes up into the spinal cord just behind the head. “Lameness is, of course, an economic concern for feedlots because of the cost of medications and labour to care for the animals, but it’s equally an animal welfare concern because many lameness conditions are very painful and may become chronic,” Jelinski says. “Unfortunately, we can’t do much to manage the pain. Unless we know the condition has a chance of improving with appropriate treatment, it’s best to deal with it by early marketing or euthanasia.” c
digital dermatitis
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