Growing Beef Newsletter
March 2025, Volume 15, Issue 9
The Copper Conundrum
Jacob Henderson, PhD student, and Stephanie Hansen, professor, Iowa State University
We all know that copper is worth a lot. People wouldn’t steal it from air conditioning units if it wasn’t. But what is copper worth in cattle? It’s a great question, and the answer isn’t as clear-cut as you might think.
Let’s start with what we do know. Copper is an essential trace mineral, supplied in very small amounts to support a wide variety of functions involved in everything from the reproductive system, to mounting an immune response, to building the connective tissue needed for optimal growth. The NASEM copper recommendation for beef cattle is 10 ppm for the total diet (not supplemental) at all production stages.
Surveys from the 1990s revealed that forages in the largest cow producing areas of the country are often copper deficient (less than 4 ppm) and contain copper antagonists, which tightly bind copper in the rumen and make it completely unusable to the animal (Corah and Dargatz, 1996). Unsurprisingly, many of these cows were found to be copper deficient.
Mineral supplementation strategies vary widely depending on what the circumstance of the producer allows. Some cows on open range may never see mineral, but in other settings, mineral supplementation may be heavily managed. To the fault of no one, this has resulted in cows (and the calves being born to them) that might range from clinically deficient to well beyond adequate liver copper stores, but producers don’t have an easy way of knowing where their animals fall on this spectrum since the best way to assess copper status requires a liver biopsy.
Because deficiency is always a concern and it’s difficult to know what a ruminant’s true copper status is, many feedlots understandably take a “better safe than sorry approach” and supplement well in excess of NASEM recommendations. A survey of feedlot nutritionists found that most supplement copper at 17-20 ppm; however, this may not be the right solution.
Unlike monogastric animals that readily excrete excess copper, ruminants have minimal capacity to do this. Instead, the ruminant liver soaks up copper like a sponge, and liver copper stores increase proportionally to dietary copper. While most veterinarians consider 125-600 ppm of liver copper to be “safe” for cattle, studies actually suggest that as little as 450 ppm of copper in the liver can cause oxidative damage (Strickland et al., 2019). It has become increasingly common to see calves entering the feedlot with that much or more liver copper, especially beef on dairy crossbreds, which come from a dairy industry that has been battling excess copper intake for several years.
The weak immune system of these dairy-beef calves and their commonly excessive liver copper stores prompted us to investigate whether or not over-supplementing copper might be contributing to the poor health of these calves when they enter the feedlot. This study was funded by the Iowa State Beef Checkoff in collaboration with Dr. Jodi McGill. As it turns out, steers with excessive liver copper (this group of calves averaged just over 600 ppm liver copper, which is in line with what has been seen in the industry) actually do experience heightened severity of disease compared to calves with 250 ppm liver copper when infected with BRD. We scored them daily over the course of disease based on depression, appetite, and respiration, and we also intermittently conducted ultrasound on these animals to look at the level of consolidation (mucus buildup) in the lungs. We saw that the calves with excess liver copper experienced much sharper increases in their clinical disease scores and remained higher throughout the course of disease than the calves with adequate copper. We also see that, while all steers experienced increased mucus buildup in the lungs over the course of disease, the steers with high liver copper tended to have greater lung consolidation overall. All of this goes to show that over-fortifying diets with copper may have negative impacts on the health of these dairy-beef calves.
Admittedly, the dairy-beef situation is on an extreme end of the spectrum, and the majority of native beef cattle wouldn’t reach the same harmful liver copper concentrations. Despite this, we have evidence that even relatively minor differences in copper status can have impacts on how cattle respond to growth enhancing technology such as implants and beta agonists. Messersmith et al. (2021) grouped steers by their liver copper into low, medium, and high copper treatments, and fed half of the steers in each treatment the beta agonist ractopamine hydrochloride (300 mg/steer/day) to determine how their copper status impacted the growth response to ractopamine. The best response to beta agonist was in the medium group, while the low group had zero response to ractopamine, and the high group has less than half the performance gain of adequate group. We then conducted a follow-up study, which showed that as long as cattle have adequate liver copper stores, they mount a response to ractopamine even when no copper is supplemented in the diet. Of the steers that had very low liver copper stores, 5 ppm of dietary Cu was enough to support their ractopamine response (Messersmith and Hansen, 2021).
Thus, it seems quite possible that we are stealing performance by supplementing cattle with 17-20 ppm copper. The NASEM recommendation of 10 ppm dietary copper already accounts for a moderate amount of antagonists present in the diet as a “fudge factor”, so doubling this requirement may be unnecessary. In fact, our data suggests that 5-10 ppm is likely closer to the true requirement of these animals, and anything in excess may be hurting performance.
More research is needed to refine copper requirements at different production stages, but one thing is clear: when it comes to copper, more isn’t always better.
References
Corah, L. R., and D. Dargatz. 1996. Forage analyses from cow/calf herds in 18 states.
Messersmith, E., M. Branine, O. Genther-Schroeder, J. McGill, and S. Hansen. 2021. Initial liver copper status in finishing beef steers fed three dietary concentrations of copper affects beta agonist performance, carcass characteristics, lipolysis response, and muscle inflammation markers. Animals. 11. doi:10.3390/ani11092753.
Messersmith, E. M., and S. L. Hansen. 2021. Effects of dietary copper supplementation on performance, carcass characteristics, and lipolytic rate of beef steers fed ractopamine hydrochloride. In: Translational Animal Science. p. S96–S100.
Nutrient Requirements of Beef Cattle, 8th Revised Edition. 2016. 8th ed. NASEM, Washington, D.C.
Strickland, J. M., T. H. Herdt, D. G. Sledge, and J. P. Buchweitz. 2019. Short communication: Survey of hepatic copper concentrations in Midwest dairy cows. J Dairy Sci. 102:4209–4214. doi:10.3168/jds.2018-15566. Available from: https://doi.org/10.3168/jds.2018-15566
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