Unrecognized mineral status insufficiency (subclinical deficiency) is difficult to detect. Figure 1 (click to enlarge) depicts the effects of trace mineral deficiencies in cows and calves. A mineral deficiency first impacts the immune system. Subtle effects on immunity often go undetected. Slow growth rate and/or poor reproductive performance may also be a result of insufficient mineral intake. Because health challenges and poor performance can be influenced by many factors, the mineral status of a herd may often be overlooked.