Digital dermatitis a concern at most dairy farms

Kimberly - When it comes to the treatment of digital dermatitis in cattle, “less is more,” according to University of Wisconsin – Madison school of veterinary medicine associate professor and epidemiologist Dorte Dopfer.

But Dopfer wishes that much more awareness would exist about how early the heel bacterial disease can strike dairy cattle – heifers well before they calve in too many cases. Unfortunately, she also realizes that the ailment “is here to stay” on many dairy farms.

A native of Germany and United States resident since 2008, with experience on dairy farms in several other countries, Dopfer was a presenter at the recent “Raising Quality Dairy Heifers” programs sponsored by the Extension Service's dairy team. She has had an intense interest in coping with digital dermatitis for 25 years.

According to national statistics, 70 percent of the dairy operations in the United States have a digital dermatitis presence. In herds of at least 500 cows, the incidence rate is 95 percent.

Disease background

Dopfer pointed out that digital dermatitis, which is a disruption of cell growth in the heel, was first identified in Europe during 1970s. (Online information indicates the first discovery was in Italy in 1974.) The first identification of it in the United States occurred in 1980, she noted.

Farms can be placed into three categories or type regarding the disease – free of it, a single outbreak, and a chronic status of infection, Dopfer suggested. She also applies the three type designation to dairy cattle on their vulnerability to the disease.

In the terminology which applies to digital dermatitis, there are four main stages – M1 to M4. In order, they are the appearance of the first small red lesion on the back of the heel (most often on the back foot), the acute and painful outbreak, the healed brown scab, and the chronic stage characterized by puppet or mushroom growths which can result in new outbreaks.

Tackling the task

If Dopfer had her way, all dairy cattle would be tested for whether they have a pre-disposition to be infected with digital dermatitis. To her surprise and that of others, such a trait was verified with research in Europe. Dopfer realizes that tagging sires with that undesirable trait would not be popular.

Among the consequences of the infectious disease are the loss of milk production, an average delay of 24 days until a subsequent pregnancy, the costs associated with treatment, and probable early involuntary culling of infected cows, Dopfer observed. The first incident often occurs among pre-calving heifers because “no one is looking” for the physical symptoms of the disease, she remarked. Dopfer indicated that it takes about three weeks from exposure to the digital dermatitis pathogen for an infection to begin.

In tracking the origin of an outbreak, particularly among heifers, the hygiene practices and any incidents in the prior 60 to 90 days are probably responsible, Dopfer indicated. One contributing cause that needs to be avoided are handling practices which cause cattle to slip on concrete floors, she emphasized.

Prevention practices

Rather than being burdened with treatment of infected animals, Dopfer wishes that outbreaks be prevented. Among the practices she listed for achieving that are keeping cattle (even those on pasture) out of mud and manure, avoiding the cross traffic of cattle, equipment, clothing, and other items that could spread infectious agent, and the use of properly constituted and managed footbaths to help keep the feet of dairy cattle clean and healthy.

In addition to the cattle owners and daily caretakers, Dopfer said that hoof trimmers are crucial to both the identification of the disease and to its treatment. The best chance for a successful treatment and for breaking the M1 to M4 cycle is with the first topical treatment and do it immediately after the first physical sign of a still small reddish and gray lesion, she emphasized.

Hoof trimmers should not be trying to remove the infectious lesions, Dopfer cautioned. Rely instead on topical treatments for which a good sign of success is the falling off of the flaps of excess skin tissue which often accompanies an infection, she explained.

During trouble-shooting ones, including one to a large herd in Virginia, Dopfer has encountered treatment efforts that will never be successful. She described such ineffective practices as a far too acidity footbath and much too late topical treatment.

Treatment protocol

In tune with her theme is “less is more” in controlling digital dermatitis, Dopfer said “less applied early is more” in the initial treatment of lesions on the back of an animal's heel. By that, she means that the topical treatment should not consist of caustic and acidic substances that often “do more harm than good.”

A proper topical treatment is a non-antibiotic product, among which chlorine, dish wash detergents, tetracycline, and clean water are acceptable, Dopfer advised. If treatment doesn't occur until the M2 acute stage, the hoof pouch needs to be cleaned, filled with gauze, and covered with no more than two grams of tetracycline before a wrap is applied, she stated.

The same “less is more” point applies to the application of a wrap after an initial treatment, Dopfer continued. In order to allow the wrap to fall off after a day or two, avoid the temptation to have more than one round on the wrap, she said.

Footbath prescription

In many cases, it is appropriate to have the cattle walk through a footbath up to three days per week as a way to maintain hoof health, Dopfer noted. She said that unit should be 10 to 12 feet long – sufficient for two placements of the feet on each trip – with front entry board height of 10 to 12 inches along with no shadows or intervals of dark and light.

What's in the footbath is just as important as its conformation, Dopfer stressed. Because the natural pH on a cow's skin is between 3 and 7, the footbath solution should not have a pH of lower than 3, she pointed out. She realizes it is not a pleasant message but she calls for the routine use of footbaths.

Among the footbath disinfectants that Dopfer finds acceptable are bleach, dish wash detergent, chlorine, a 2 to 5 percent concentration of copper sulfate, and 37 percent formalin provided that 3 gallons of the raw product are diluted with 97 gallons of water.

If necessary, buy pH indicator paper to test the pH level of the solution, Dopfer said. As a aid on the limit of cow trips that can be accommodated before a new solution is needed, she noted that the Extension Service has a kit that can answer that question.

Management practices

During trouble-shooting trips, including one to a large dairy herd with a seven year history of infection, Dopfer has encountered a variety of treatment efforts which she is convinced will never succeed. As an overall approach to digital dermatitis, Dopfer recommends starting with frequent monitoring of pre-calf heifers.

Depending on the possibilities at a particular dairy facility, it might be appropriate to keep infected cows in a separate group or even to separate heifers according to any tested pre-disposition of being candidates for a digital dermatitis infection, Dopfer observed.

Dopfer reminded everyone concerned with digital dermatitis that the disease is three-pronged – a combination of human, animal, and environmental influences. She can be contacted by e-mail to dopfer@wisc.ed.