Analyzed concentrations of iron in porcine and human milks, as well as in dietary treatments during both phases of the pig study. During phase 1, pigs were fed either a control (CONT) or iron-deficient (ID) milk replacer. The CONT treatment contained 21.3 mg/L (106.3 mg/kg), and the ID treatment contained 2.72 mg/L (13.6 mg/kg). The ID treatment closely resembled the average iron content of porcine milk (n = 7; 1.06 mg/L) collected during a prior study [18], and is comparable to the iron concentration of human milk [7,19]. During phase 2, all pigs were fed a series of standard commercial starter diets (180–300 mg/kg). Abbreviations: CONT, control; ID, iron deficient; PND, postnatal day.