There seems to be a lot of confusion in the dairy industry about the ability to benefit from an anaerobic digester and still use copper in a hoof care program.
As of April 2021, there were more than 221 digester systems processing dairy manure in the U.S. Being based in California, I’ve had the opportunity to work with numerous dairy farms using digester technology as it’s increased in usage over the last five years. I currently work with over 60 dairies benefiting from digester technology while running liquid copper through their hoof bath. In this article, I will share some key insights on how dairy farms can profit from both copper footbath solutions and anaerobic digester technology. Along the way, I’ll share some blind spots to watch for.
Do your digester research
There are numerous types of digester systems available. The most common systems are plug flow digesters, followed by complete mix digesters and covered lagoons. While some dairy farms can install and operate their own system, others have found it more beneficial to sell their manure to companies that own and operate the digester.
As an industry, we are still at the front end of anaerobic digester technology, so the amount of scientific research available to determine best practices is limited. There is, however, one study that has been published by the American Society of Agricultural and Biological Engineers on the effect of copper sulfate. The study found that a small amount of copper is beneficial to the anaerobic digestion process (1-10 milligrams per liter), but increasing concentrations can be inhibitory (20-40 milligrams per liter) and even toxic (100 milligrams per liter). It’s not surprising to learn that too much of a good thing is harmful, but knowing where these thresholds are is the key (Table 1).
The antimicrobial benefits of copper have been known for centuries. Several university studies have demonstrated the effectiveness of copper sulfate in managing hoof rot and digital dermatitis. The last thing any savvy farmer wants to do is disrupt what’s working well to try and benefit from something new. By thoroughly researching all the different choices, a dairy can best determine which anaerobic digester option is most conducive to the unique setup of their facility and the other products and technologies they currently rely on, including copper in the hoof care program.
Manage your total copper inputs
Copper sulfate can accumulate in the manure from many sources on the dairy, not just the footbath. It’s important for dairies to monitor all the copper inputs, from the footbath to the ration, and measure the total parts per million (ppm). This can be as easy as asking your copper supplier if they know the range for both daily and weekly usage and ensure your digester is receiving just the right amount of beneficial copper.
It's important to understand that copper, just like digesters, comes in many different forms and concentrations. Each form will break down differently, and thus impact the levels in the manure differently. If your copper levels are too high for a digester, then you need to evaluate the type and source of your copper. There are many copper choices and suppliers for both the feed ration and the hoof health program.
For example, there is an acidified liquid copper that can be used in footbaths. We analyzed the amount of copper left in processed water when using acidified liquid copper for one day and for one week to verify that the trace amounts were within the beneficial range.
The properties of this liquid acidified copper, and the impact on the footbath and manure, are visibly different than those of a dry bagged copper product. If powder copper isn’t thoroughly mixed with water, it can leave large undissolved clumps behind in the footbath. This undissolved copper does nothing to benefit cows' hooves and has much more potential to negatively impact a digester if it doesn’t break down before it enters the digester system.
If a dairy finds that the copper levels in their manure are higher than the beneficial range for a digester, they can maintain the hoof care program by switching to a different copper product or supplier confirmed to be within the beneficial range. This way, the dairy can still maintain copper in the hoof care program and utilize an anaerobic digester.
Consult with trusted advisers
It is achievable for dairies to benefit from a digester and keep copper in their footbath program. Before you commit, do your research to figure out the best digester option, understand the amount of copper in your manure and get connected with other dairies successfully using both to learn from their experience.
References omitted but available upon request by sending an email to an editor.
