Seeing a reddish hue on the coat of a black cow in late winter, it’s not unusual to wonder if that shade is normal or is due to a copper deficiency. Low forage copper and high levels of molybdenum in forage and sulfates in water are common in the Northern Great Plains, therefore you may be right to wonder. Copper is important for several functions in the body related to immunity, growth, and reproduction and deficiencies of this mineral can result in poor response to vaccinations, susceptibility to disease, slowed growth, bone problems, diarrhea, and poor reproduction. Therefore, it may be worth the effort to evaluate the potential for copper problems on your operation.
The basic requirement for copper for beef cattle is 10 parts per million (ppm; or mg/kg) per day, but this level may not be adequate if there are high dietary levels of molybdenum (more than 2 ppm) or sulfur (more than 0.25%). A number of studies in the Northern Plains have reported forage copper concentrations of less than the 10 ppm recommendation in both native and seeded grasses. In addition, forage molybdenum concentrations of greater than 2 ppm are common and, in some areas, sulfates may be high in water. These complicate the copper picture.
Primary copper deficiencies, due only to low dietary copper levels are easily overcome by adding copper to the diet, often in a trace mineralized salt mix. However, many observed copper problems are due to secondary deficiencies. Copper interacts with a number of other elements, and it is important to be aware of these to understand how to avoid copper deficiencies in cattle. Secondary copper deficiencies are due to an inability of copper to serve in its normal functions because it may for a complex with other compounds, or antagonists.
Table 1 shows levels of sulfur, molybdenum and iron that cause antagonism with copper and can affect cattle health and performance.
These antagonists form complexes with copper that may be found in blood, making blood copper levels a poor tool for diagnosing a copper deficiency – there may be adequate amounts of copper in the blood, but it may not be useable by the animal. A copper containing protein in the blood, ceruloplasmin, is a reflection of blood copper that is available for use by the animal and is a more useful diagnostic tool than blood copper. Liver copper levels give a better indication of the true copper status of the animal because they give a better reflection of copper that is available for use. Veterinarians can collect a small sample of liver from live animals through a biopsy. They will want to sample several animals (often 4 to 7) to get an estimate of the herd copper status.