Speciation analysis of manganese against the background of its different content in the blood serum of dairy cows

Studies in the field of microelement speciation in the body of farm animals, in particular dairy cattle, are almost completely absent. The average concentration of Mn in the blood serum of all the studied animals (n = 80) was 2.5 μg/L, which corresponds to normal values. Of the total number of animals, 21% were the cows with the low normal values (serum Mn concentration ≤ 2 µg/L, i.e. less than Q₂₅ of the total sample) and 25% were the animals with the high normal values (serum Mn concentration ≥ 2.72 µg/L, i.e. more than Q₇₅ of the total sample). The data obtained in the course of the study indicate that the change in the Mn level, even in the range of normal values, is accompanied by the redistribution of this element over various protein fractions. The six found Mn blood serum forms are presumably represented by α2-macroglobulin (tetramer, dimer, and monomer), transferrin/albumine, manganese citrates, and “free” metal ions. The analyzed fractions of Mn found in the blood serum of cows had the following hierarchy of concentrations: in the group with low-normal values of Mn (“free” Mn >> tetrameric form of α2-macroglobulin >> transferrin/albumine >> dimeric form of α2-macroglobulin >> monomeric form of α2-macroglobulin >> citrate), in the group with high normal manganese values ("free" Mn >> monomeric form of α2-macroglobulin >> transferring/albumine >> citrate >> tetrameric form of α2-macroglobulin >> dimeric form of α2-macroglobulin). In the group with high normal Mn values relative to the group with low normal values, there was a percentage decrease in the tetrameric fraction of a2-macroglobulin from 17.2 to 4.4%, dimeric fraction of a2-macroglobulin from 6.9 to 2.2%, “free” Mn from 54.3 to 44.4% and an increase in monomeric fraction of a2-macroglobulin from 6.7 to 23.1%, transferrin/albumine from 10.1 to 17.7%, citrate from 4.8 to 8.2%. Our data demonstrate the features of Mn redistribution of dairy cows, which can be used for an extended assessment of the microelement status of animals.