Proper footbath management has long-term environmental implications
Adaptation is commonplace on the farm. The weather changes, we adapt by changing our attire and adjusting. Sooner or later a new season will arrive, and we’ll need to adapt again. In some cases, adaptation becomes a permanent change. One change farmers have implemented on their operations is managing digital dermatitis (DD), or hairy heel warts.
Thirty years ago, DD was uncommon on US dairies. But as farms grew bigger and smaller herds combined to form larger herds, DD began to spread rapidly around the country. Adapting to DD became a permanent management change.
Incurable but manageable
Digital dermatitis is incurable, but it can be managed. Footbaths are an important tool utilized to prevent animal lameness, limit the spread of DD, and maintain hoof health on dairy farms.
According to a 2015 survey of 45 eastern Wisconsin dairy farms, 75 percent of the farms utilized footbaths to promote hoof health and animal productivity, and longevity. The same project, which was conducted by eastern Wisconsin Extension Agriculture Educators, determined copper sulfate was the most used footbath disinfectant in the region, due to both its relatively low cost per animal treated and effectiveness in reducing the incidence and severity of hoof lesions.
More than 65 percent of the 45 surveyed farms utilized copper sulfate in their footbaths, with 33 percent of farms using a footbath four to seven times a week, and 27 percent using a 12 to 30 percent copper sulfate solution.
While copper sulfate is a low-cost effective solution to manage DD, what happens to it after disposal? Most farmers dump spent solution, which is then washed into the manure storage. A typical footbath holds 40 to 50 gallons of solution and should be changed after 150 to 300 cows walk through it.
Take, for example, a 250-cow herd that would use one fill of solution per treatment. Using the UW-Madison School of Veterinary Medicine’s recommended practice of treating cows four times per week, that equals 1,000 gallons of waste copper sulfate per week. This scenario adds 52,000 gallons of copper sulfate solution to the manure storage per year. Copper sulfate concentration varies per farm, but typically it is two to five percent.
After the contents of manure storage are applied to fields, it provides nutrients to plants. As copper is utilized in small amounts by plants and is not readily leached from the soil, it can accumulate within the soil profile, particularly with regular, long-term applications of dairy manure containing copper footbath materials.
Such applications can significantly increase copper to toxic levels in plants and soil. According to Texas A&M University, the toxic levels raise several concerns for dairy farmers:
- Excess soil levels may reduce crop yields.
- Forages grown in excessive copper level soils may be toxic to livestock.
- Recycling (applying manure from cattle who ate excessive copper-rich feedstuffs) back to the field escalates copper loads in soil and forages.
- Improper footbath management may not comply with nutrient management plans or environmental permits.
Substantial research has not been conducted on the impact excessive copper has on livestock. However, secondary issues are beginning to present in dairy cattle that could be tied to copper sulfate footbath solution being applied to forage crop fields. An extensive review of Wisconsin Veterinary Diagnostic Laboratory (WVDL) accessions along with the results of slaughterhouse surveys indicate that copper is accumulating in the livers of Wisconsin Holsteins of all ages.
More research needs to be completed to understand the impact copper sulfate footbath management has on the health of livestock, soil, and forages. Footbaths should be managed according to recommendations to manage DD, but also reduce the negative impact it has on virtually every part of dairy herd management. It’s not just a problem that gets washed down the drain, it is a long-term management practice.
Aerica Bjurstrom is the Regional Dairy Educator for Kewaunee, Brown & Door Counties, UW-Madison Division of Extension