James, B. E., Hendry, P. G., and MacMahon, R. A. (1979), Aust. Paediatr. J., 15, 67-71. Total parenteral nutrition Of premature infants. 2. Requirement for micronutrient elements. By using metabolic balance studies we have investigated the ability of 5 small premature infants, fed intravenously with a formula based on L amino acid isomers, to retain 5 essential micronutrients (Fe, Zn, Cu, Mn, Cr).For each element there was a significant correlation between the input and retention and, by analogy with fetal growth, tentative recommendations have been made for the rate of infusion of these elements into very low birthweight infants.