Abstract: A process for preparing a feed supplement that promotes growth in animals by (i) preparing a dry metal carboxylate of formula M(RCOOH)2; (ii) preparing a metal aminoate; and (iii) mixing the dry metal carboxylate and the metal aminoate under conditions that form a complex including the metal carboxylate and the metal aminoate and water, then removing the water to form a dry metal complex of the metal carboxylate and the metal aminoate. When administered to an animal in its feed, a bioavailability of the divalent metal in the dry metal complex is different than the bioavailability of the divalent metal in either the dry metal carboxylate or the metal aminoate alone.