Calves are born with a mostly inadequate essential amino acid (EAA) status. Studies were designed to test the hypothesis that delaying the intake of the first colostrum for 24 h, besides its early effects, also has late effects on plasma free amino acid levels and on the protein status. There were marked and rapid elevations (within 2 h) of plasma levels of various amino acids, and especially of EAA, after the intake of the first colostrum, whereas changes after the intake of mature milk on day 28 of life were mostly absent or concentrations even decreased. The EAA and non-essential amino acid (NEAA) status was rapidly normalized after intake of the first colostrum, but normal plasma levels of some amino acids were also reached during the first 24 h of life even when the first meal was withheld. Delaying colostrum intake had only transient effects on EAA and NEAA (except hydroxyproline), in contrast to its effects on plasma immunoglobulin G and total protein levels.