Relevance. Manganese is an element of Group 7 of the Periodic Table of Chemical Elements. In nature, it does not occur in its usual state but is present in ores in the form of oxides, hydroxides, carbonates and silicates. The main mineral containing manganese is pyrolusite, its concentration in it is 3 %. In the earth’s crust, Mn is the third most abundant heavy metal after iron and nickel (about 0.1 wt%) [2, 10, 15, 17].

This microelement is one of the few that can have eight different valence states, but it is present in the body only in the form of bivalent and trivalent compounds. The coordination chemistry of Mn² and Mg² is similar: both cations are predominantly associated with relatively weak donors, such as carboxyl and phosphate groups, and can replace each other as activators of some enzymes, as well as in complexes with DNA [1, 3, 5, 14, 21].

Manganese is necessary for plants and animals, its concentration in the former is higher than in the latter. In plants, it contributes to the formation of chlorophyll, stimulates respiration and enhances the synthesis of ascorbic acid. The manganese content in pasture grasses varies depending on the species (legumes contain less manganese than cereals), age, but mainly on soil pH. When the pH gets above 6.0, the available manganese content decreases [8, 12, 16].

Since the concentration of manganese in feed varies widely (from 5 to 120 mg/kg), and the possibility of increasing it in plants with the help of micronutrients is doubtful, the main preventive measure against manganese deficiency in animals is the introduction of manganese salts as feed additives. Foods relatively rich in manganese are beet tops, clover, bran, oilseed cake. All grain crops, both legumes and cereals, are poor in manganese [18, 20].

Currently, along with an in-depth study of the gene and phenopool of agricultural animals of different breeds and species in their breeding zones, special attention is paid to the production of environmentally friendly and safe products of the agro-industrial complex for the end consumer [6]. In this regard, water, feed, soil, organs and tissues of animals are carefully monitored for the content of chemical elements. In addition, the search is carried out for in vivo non-invasive markers characterizing the accumulation of heavy metals in organs and tissues [7, 22].