Copper concentration in dairy rations: Should we be concerned?

By Dr. Zach Sawall
A persistent concern on many dairy farms is the rising copper concentration levels in cattle liver samples. According to Dr. Jeremy Schefers, University of Minnesota Veterinary Diagnostic Laboratory, the concern stems from the common usage of copper sulfate in footbaths to control digital dermatitis and the subsequent higher copper concentrations in manure and on cropland.

In 2001, Ev Thomas of the Miner Institute reported increased soil concentrations of copper due to copper sulfate footbaths and foliar application of micronutrients, like copper. This means management of copper usage in footbaths, cropland, and dairy rations is essential for optimizing cow health and soil integrity.

Function and requirements
Copper is a key component to control many bodily functions. Some functions include building strong bones and connective tissues, supporting the immune and antioxidant systems, absorption and transportation of iron, and protection of cells from oxygen metabolites.

Dietary copper requirements vary with the age of the animal. To meet the National Research Council (NRC), 2001 nutritional requirements for dry and lactating dairy cows, rations need to contain 13 to 15 parts per million (ppm) of copper.

Excess copper will accumulate in the liver, and, during times of stress, large amounts can be released into the bloodstream, causing destruction of red blood cells and eventually death.

Copper sulfate is also a bactericide and can kill beneficial bacteria in lagoons and soil and then harm crop production by binding up vital nutrients.

Historical copper levels
Nutritionists have not traditionally tested for copper, so they rely heavily on historical values. According to the NRC, 2001, average copper concentration in legume silages is 9 ppm and 7 ppm in corn silage.

Are these values increasing with the use of copper sulfate and foliar applications?  A survey conducted in summer 2015 on 50 Wisconsin dairy farms compared copper levels in forages and TMR to find the answer.

Copper levels on farm
Of the 50 farms surveyed, 44 used copper sulfate in footbaths and four of those farms also used a foliar application with copper. Producers, on average, contributed 2.9 pounds of copper per acre per year. Since the average corn crop yield of 150 bushels per acre can only remove 0.11 pounds of copper per acre per year, according to L.G. Bundy, 1998, the copper accumulates and persists in the soil.

Copper levels in forages
Average copper levels in legume forages were 9.8 ppm and 7.7 ppm in corn silage. While these averages are slightly greater than historical values, there is a great deal of variation between farms.  The highest forage copper concentrations were found in southeast Wisconsin, indicating a possible geographic factor.

Copper levels in TMR
The average copper concentration in TMR rations was 18 ppm. The NRC, 2001 recommends, for lactating dairy cows, 15 ppm and a maximum tolerable level of 100 ppm, indicating dietary copper levels were not excessively exceeded.

In addition to variation between farms, there is also variation between dairy cattle breeds. The American Jersey Cattle Association has documented that Jersey cattle accumulate copper in the liver quicker than other breeds.

Conclusion
The survey found copper levels to be slightly greater than the current NRC, 2001 guidelines. Most farms find it difficult to eliminate copper sulfate from their farms completely, but proper protocols should be followed. Monitor copper levels in forages and soil to establish a baseline for future comparison, always mix copper sulfate at appropriate concentrations in footbaths, distribute manure evenly across land, and, if copper concentrations are elevated on your farm, it may be time to investigate alternative footbath solutions.

This article originally appeared in the August 7 issue of Progressive Dairyman.  Click here to read the full article.

About the author:  Dr. Zachary Sawall grew up on a dairy farm in northeast Wisconsin. He attended the University of Minnesota where he earned his bachelor’s degree in animal science with an emphasis in ruminant nutrition. In 2013, Sawall was named Outstanding Master’s Student by the Department of Animal Science at the University of Minnesota.  He continued there to earn his Ph.D. in ruminant nutrition.  Sawall joined Vita Plus in 2015 as a dairy nutritionist and technical services specialist in central Wisconsin. In his free time, Sawall enjoys hiking, hunting, and spending time with his wife, Sandra, and son, Jonathan, and working on their parents’ dairy farms.