Copper sulphate is a proven and well accepted method of controlling PDD.  High concentrations (5% - 10%) of copper sulphate proved effective in preventing PDD. A 5% solution is 25 lbs in a 50 gallon footbath.

Because copper sulphate is limited in solubility, the footbath must be recharged about every 200 cows, sometimes more often depending on footbath management practices.

As the chart illustrates, at a pH of 7 (typical  tap  water),  only  17.39% Cu++  is available in solution to attack the bacteria.  Solubility is a BIG problem.  Contamination, use and precipitation of 80% of the chemical will make the treatment effective for 200 or fewer cows.