Digital dermatitis (DD) goes by many different names: Mortellaro’s disease, strawberry foot rot and hairy heel warts. But the one thing everyone can agree on is how frustrating it is to see on your farm, over and over and over again – especially among heifers.

DD is one of the most common foot lesions on dairies, and the 2007 National Animal Health Monitoring System survey of U.S. dairy farms reported that 61 percent of lameness cases in bred heifers and 49 percent of lameness cases in cows were caused by DD.

This infectious, bacterial disease has a complicated cycle of development and recurrence, which leads to its frustrating nature. Suggestions for control of DD include prevention and routine treatment, mainly focusing on the lactating herd. However, even if DD is well controlled in lactating cattle, its presence in youngstock can result in continual introduction into the lactating herd.

Recently, the importance of youngstock in the dynamics of DD has been highlighted. Research from the University of Wisconsin has determined that DD in pre-calf heifers results in an increased risk of DD during the first lactation, decreased first-service conception, more days open, changes in claw conformation and decreased milk production in first lactation.

Therefore, an efficient prevention and control program should be a priority during the raising period to maximize the potential of youngstock.

Pen walks prove to be an effective way to find DD

To get DD under control on your dairy, the first step is to identify to what extent the disease exists in youngstock on the farm, and that requires a means of detection. Recently, the University of Calgary, in Alberta, Canada, conducted a research study on the use of pen walks to identify DD in pre-calf heifers.

All hind feet of 3,026 group-housed, pre-calf heifers (under 24 months old) on 28 Alberta dairy farms were scored as DD “present” or “absent” (yes or no) while moving freely in pens or while restrained in headlocks.

On five of those farms, the feet of 292 heifers were also observed in a hoof trimming chute to determine how well pen walks can identify DD lesions.

In the hoof trimming chute, lesions were scored based on the M scoring system: M0 – healthy skin with no evidence of a lesion; M1 – a small lesion (less than 2 centimeters in diameter), red to gray skin defect; M2 – an ulcerative lesion (2 centimeters or greater in diameter) with a red-gray surface; M3 – healing stage after M2 lesion surface becomes firm and scar-like; M4 – chronic stage lesion that is raised with brown or black tissue, thickened epithelium, scaly or has hair-like projections; M4.1 – recurring active M1 lesion within the boundaries of an existing M4 lesion.

Pen walks were able to correctly classify 74 percent of feet that had DD (stages M2, M3, M4 and M4.1) and 97 percent of feet that did not. That means 85 percent of animals identified as having DD using a pen walk will have DD in the trimming chute.

Pen walks are therefore reliable enough to use as a screening tool for treatment or to determine where prevention and control methods should be implemented.

How to make pen walks part of your routine

Here are some suggestions if you would like to incorporate pen walks into your regular farm routine.

Know how to identify DD

To identify DD-negative feet, you want to be able to easily see the cleft (the space) between the heel bulbs of the foot. If there is any inflammation, scabbing, proliferative hair-like growth or anything that makes you suspicious, classify that foot as having DD.

This means you will more correctly identify healthy feet compared to feet with lesions (similar to the results of the University of Calgary study).

• Train and practice: A great way to train yourself is to practice on feet in the milking parlor. These feet can be sprayed with a parlor hose and observed for a longer period of time than in a pen. If you need extra training, your hoof trimmer or veterinarian is a great resource.
  
  
• Appoint: Ideally, appoint one or two individuals in charge of scoring lesions on a regular basis. It works best if these people are already involved in activities like pregnancy checking, moving animals or hoof trimming. Make it a priority to look at feet anytime heifers are in headlocks.
  
  
• Keep records: Recording which animals and what pens are positive or negative for DD is a great way to track your progress and determine if any implemented control methods are working.
  
  In the research outlined above, data was handwritten; however, a Zinpro DD Check app for smartphones exists that can be used for entering data and tracking progress at a cow level, complete with pictures of different lesion stages and definitions.

If you make it a priority to walk through pens prior to scheduled hoof trimming (perhaps even with your hoof trimmer), this will provide an opportunity to screen individual animals or groups for treatment. This is also a great occasion to discuss with your hoof trimmer about incorporating DD control methods to your youngstock.

Dörte Döpfer, from the University of Wisconsin, suggests that preventative methods (footbaths, foot sprays) should be implemented in the group 60 to 90 days younger than the group in which DD is first identified.

Therefore, pen walks can be used to determine which groups and individual animals have DD lesions so that preventative measures can be targeted to the groups that need it, and specific animals can be screened for treatment. If this is done routinely, DD lesions will likely be managed effectively, and consequences of those lesions will be minimized in the future.  PD

Casey Jacobs is a Ph.D. student at the University of Calgary Faculty of Veterinary Medicine (Calgary, Alberta, Canada) studying farm management of digital dermatitis. Email Casey Jacobs for more information on this or other research projects.

References omitted but are available upon request. Click here to email an editor.

PHOTO 1: DD-negative feet: The cleft between the heel bulbs is easily distinguished. There is no evidence of any lesions.

PHOTO 2: DD-positive feet: Extra hair growth, inflammation and the cleft between the heel bulbs is difficult to distinguish. Photos provided by Casey Jacobs.

• Casey Jacobs

• Ph.D. Candidate - Veterinary Medical Sciences
• University of Calgary
• Email Casey Jacobs