A method of enhancing the growth of an animal, as well as treating or preventing antimicrobial infections is provided. The method includes causing the animal to ingest or absorb an effective amount of one or more Fe III complex compounds, including but not limited to Fe III complexes comprising ligands bound to the iron center such as amino acids or α-hydroxy acids. The compounds are also useful for inhibiting, reducing, or preventing biofilm formation or buildup on a surface; the treatment of, inhibition of growth of, and inhibition of colonization by, bacteria, both in biological and non-biological environments; disinfecting surfaces, potentiating the effects of antibiotics and other anti-microbial agents, and increasing the sensitivity of bacteria and other microorganisms, to anti-microbial agents are also provided.