Novel supplemental guidelines for Zn, Cu, and Mn, in bovines, by integrating net requirements, native dietary occurrence, and the boundaries of homeostatic regulation

A long-standing objective in ruminant nutrition is to ensure an adequate supply of the key trace metals Zn, Cu, and Mn, while accounting for bioavailability, nutritional interactions, and not exceeding tolerance. In practice, however, dietary supplementation often by far exceeds reference nutritional guidelines, largely as a precaution against the multiple uncertainties of trace mineral supply. Current reference recommendations are determined using fixed and highly conservative uptake coefficien