|This article appeared in the August 2001 issue of
the "West Virginia Farm Bureau News, WVU Update."
The importance of mineral supplementation and nutrition is underestimated by most beef producers, While subclinical deficiencies often go unrecognized, they cause a reduction in growth and efficiency and depress the immune system. Trace minerals are required for metabolism of nutrients, reproduction, immune response, and nerve conduction. Deficiencies occur because cattle cannot consume enough of the minerals or because a dietary antagonist, such as sulfur or iron, is inhibiting their utilization of a trace mineral.
The most deficient minerals in grazing cattle are phosphorus, copper, and zinc. In addition, West Virginia pastures typically are marginal to deficient in selenium. Cattle here should receive supplemental selenium because it plays a vital role in the reproductive and immune systems. The importance of phosphorous is well understood, but we are just beginning to understand the importance of copper and zinc.
These two minerals, when consumed in forages, do not seem to be highly available to the animal. Therefore, even if a forage analysis shows adequate levels of copper and zinc, subclinical deficiencies can and do occur. For example, it is estimated that the absorption of copper from fescue by cattle is low, normally ranging from 5% to 15%. The importance of these minerals seems to be enhanced when cattle are stressed. There are indications that when cattle are stressed, the excretion of zinc from the body doubles and that of copper quadruples.
Weaned calves normally experience stress, which increases their susceptibility to infectious diseases. It is critical to provide adequate levels of zinc and copper to calves at least 45 days before weaning and during weaning. Maintaining adequate levels of these minerals significantly reduces the number of deaths and improves the recovery rate of infectious bovine rhinotracheitis (IBR)-stressed cattle. IBR is a problem throughout West Virginia.
The effectiveness of vaccines will be reduced if cattle have a subclinical deficiency of these trace minerals. In addition, wormy cattle have less ability to build an adequate immune system, even when effective vaccines are being used systematically. Examine the tag on your mineral supplement and look for copper sulfate and zinc oxide or zinc sulfate because these are highly available to the animal. At a minimum, it appears that when minerals are consumed at a level of 2 ounces per head per day, the mineral should contain at least 1,000 ppm copper and 2,500 ppm zinc.
If your calves experience pinkeye, watery eyes, foot rot, or respiratory problems, you should examine your mineral supplementation program.