Definition of quality parameters and chemical composition of feeds, evaluation their nutritional value and composing on this basis optimal rations for high productive animals are the most significant conditions for their health and production. More often metabolism disorders registers in the conditions of intensive animal production, at high dairy efficiency and intensive fattening. At animals at disorder of key parameters of technology (unbalanced feeding, hypodynamia, lack of insolation) is broken metabolism, decreases natural resistance, goes down quality of production that conducts to disease, premature culling and to the compelled slaughter of animals. On frequency these diseases occupy on the average 10% from all noncontagious diseases, and on dairy complexes with industrial technology and in specialized feeding economy at intensive cultivation on their share it is necessary over 30% of a noncontagious pathology. Today the control of rations on such indicators, as dry matter level, quantity of exchange energy, the maintenance of a crude and digested protein, amino acids, sugars, starch, cellulose, fat, macro-and microelements, vitamins, and also sugar-energy-protein and calcium-phosphoric parities, acid-base balance has got special value. The lack of those or other nutrients causes infringement of a clinical condition of animals and reduces their efficiency. Among the most widespread diseases of the animals registered in animal industry: cattle ketosis, osteodystrophy, endemic struma, hypomagnesiemia tetany, pasturable tetany, microelementosis, hypovitaminoses A and Е.

Belarus is among regions, where the selenium content in soil, hence, in cereal and other cultures considerably below requirements that leads to insufficiency of this microelements in a diet as the person, and animals. Synthesized in the All-Russian Scientific Research Institute of Physiology, Biochemistry and Feeding of Agricultural Animals new organic compound of selenium - selenopyran on variety of criteria has no analogues in the world among considerable quantity selenium of containing preparations and favourably differs from all known forms of microelements. Selenopyran, brought in fats and forages, shows antioxidatic the properties which are not conceding traditionally applied in veterinary science and medicine to antioxidants. Arriving in animal body with forage or in the form of injections, selenopyran is capable to play a role of a metabolic regulator. It activates enzymes of antioxidatic body protection, reduces formation new and will neutralize of earlier formed activeproducts of peroxide lipids oxidations, improves functioning of cellular membranes, normalizes metabolism, makes active cellular, humoral and phagocytal immunity links, raises nonspecific resistance and efficiency of animals. Toxicity of selenopyran more low, than at all known organic connections of selenium, and more than in 100 times is less, than at sodium selenit. The data allow to expand possibilities of application of organic selenium and to use it as a preparation raising resistance and body viability at the expense of the patronage of cellular structures from influence of oxidizers and free radicals, to normalize metabolism and to stimulate thus the big additional body weight at animals. The influence of medicine organic selenium on piglet bodies what are behind a growth and development is shown. The results showing the dynamical changes of haematologicals, physiologicals and biochemicals indices under the influence of selenopyran was given.