When it comes to lame cattle, do not make assumptions
Anybody who has raised cattle for any length of time has probably had to deal with lame cattle. The odds are great that the animal was either suffering from foot rot or a physical injury to the leg or foot. However, in the last decade, a relatively new disease has been appearing in beef cattle operations, causing issues for both cattle and their owners.
This disease, which continues to grow in frequency, is called digital dermatitis (DD), commonly referred to as hairy heel warts. Despite the keen observations of cattle caretakers, it can be difficult to correctly diagnose which disease is being presented by the animal at the farm or feedlot level. Unfortunately, there are numerous producers who have spent a lot of time and money treating foot rot over the years, only to find out the problem was actually digital dermatitis.
Foot rot versus digital dermatitis
Cattle suffering from foot rot or digital dermatitis will both exhibit lameness. However, the etiology of these diseases varies drastically, and the treatment options also differ considerably. Unfortunately, treatment options for foot rot are not effective for DD and vice versa. Correctly identifying which disease is present is absolutely critical for helping the animal get on the road to recovery.
Both diseases are ultimately caused by bacteria. Foot rot can be caused by a combination of Fusobacterium necrophorum, Bacteroides melaninogenicus and Dichelobacter nodosus, with F. necrophorum being the primary culprit. It is a naturally occurring bacteria in the cattle’s digestive system and can survive in the soil for a long time (up to 10 months). In foot rot, it is common to observe the skin split between the claws of the hoof and for pus to be present. All these bacteria cause a breakdown of the tissues, starting first with skin tissue. If not treated, that breakdown can progress to connective tissue and joints, leading to septic arthritis.
The cause of DD is not as straightforward. Bovine DD was first described in 1974, but it wasn’t until 14 years later that the first report of specific bacteria associated with the disease was made. These bacteria belong to the species treponema. They are anaerobic and seem to thrive deep in the skin. Efforts to induce DD lesions in research settings by applying active lesions to sterile feet have largely failed over the years. The first successful attempt to induce DD was made within the past two years at the University of Wisconsin. Treponema has been shown to cause disease by impairing the innate immune system and preventing macrophages from completing wound healing. There have been numerous other organisms suspected of causing DD, but to date, a clear cause and effect has not been established.
Risk factors
Cattle’s susceptibility to foot rot or DD shares some similarities. Both diseases seem to be seasonal, with the highest incidences coinciding with wet conditions. Occurrences of both diseases also spike in the fall. Any time an animal undergoes a stressful event (i.e., weather, shipping, ration changes), the opportunity for one of these diseases to take hold increases. The bacteria that cause these diseases cannot enter the skin by themselves; there must be an insult to the skin that provides an opening for the bacteria. This is why occurrences of both diseases go up when cattle experience wet conditions or very muddy pens.
Both diseases also seem to cause more issues when animals are bigger. Animals of any weight may experience foot rot if the skin barrier is broken and the bacteria are able to penetrate. It certainly looks worse to have a 1,400-pound steer hobbling around from foot rot compared to an 800-pound steer, but the likelihood that either will develop foot rot is roughly equal. In contrast, DD in cattle and the severity of the disease seems to increase as the cattle get larger. In feedlots, problems with mobility caused by DD do not seem to be an issue until the cattle are larger than 1,000 pounds. If younger, lighter cattle have it, it’s usually subclinical and not obvious. Without direct observation of the foot, producers will probably not even notice it. However, this may be the most beneficial time to address the issue.
Treatment contrasts
Foot rot appears in cattle relatively quickly, sometimes almost overnight. DD consists of chronic lesions that develop over time. Foot rot treatment is relatively straightforward, with most producers opting to use injectable antibiotics. It is advised that the foot be cleaned and disinfected as well. The recovery period is usually just a couple of days. If the animal doesn’t recover quickly, it is not “just foot rot,” and additional inspection is warranted.
Treatment of DD is not as simple. Injectable antibiotics are not effective. Topical application of antibiotics to the DD ulcer has shown to be effective but very time-consuming. Foot rot is also more likely to be treated on an individual animal basis. An operation with prior experience of DD should be proactive in treating whole pens at lighter weights to prevent chronic stages of the lesions. This presents additional challenges, as we have to treat whole pens and not just individual animals.
Footbaths are a common way to treat entire pens. The footbath is filled with water and a medicated compound. Formalin and copper sulfate are the most common compounds used. The concentration of each is of the utmost importance when first setting up the footbath. Formalin is a carcinogen, and the correct personal protective equipment must be used when employing this product. To keep each footbath at an effective level, the number of animal passes needs to be established. If too many animals are run through and the footbath becomes inert, a producer will likely spread more DD than they will prevent.
DD will continue to be a problem
History shows us that once DD appears on a premise, the likelihood that it will go away is basically zero. If you have had the misfortune of having it, think about ways to minimize its impact on your operation. Footbaths and precise standard operating procedures will likely be your best bet. A recent study at the University of Wisconsin was the first to induce DD in naive animals by applying active lesions from other animals. The researchers also looked at feeding a postbiotic that naturally primes the animal’s innate immune system. The animals that were fed the postbiotic were less susceptible to developing DD and were quicker to recover if they did. This is something to consider as a way of reducing inflammation associated with DD lesions.
