Investigation of acute and subchronic (chronic) toxicity of complexinates of trace elements in experiments with calves was realized in the conditions of the Republic of Belarus. The realized experiments were based on developed in Belarus veterinary preparations for the treatment and prevention of diseases connected with disorders of trace elements exchange containing chelate compounds of trace elements with sodium ethylene diamine acetate: Cuprovet (on the basis of CuNa); Cobalvet (on the basis of CoNa), Zinkovet (on the basis of ZnNa), and Feravet (on the basis of FeNa). There were the following indexes of ferrum in nephros - 55,3 +/- 2,26, in muscles - 134 +/- 26,6 mkg/g, and in liver - 565 +/- 35,5 mkg/g after administration of Feravet. There were the following index of zinc in nephros - 56,3 +/- 2,64, in muscles -25, 8 +/- 1,23 and in liver - 84,4 +/- 3,29 mkg/g after administration of Zinkovet. There were the following indexes of cuprum in nephros - 4,1 +/- 0,325, in muscles - 2,33 +/- 0,117, and in liver - 12,3 +/- 1,12 mkg/g after administration of Cuprovet. There were the following indexes of cobalt in nephros - 40,35 +/- 2,29, in muscles - 12,5 +/- 0,98, and in liver - 126,5 +/- 10,45 ng/g after administration of Cobalvet. Parameters of toxicity of all preparations were by the example of laboratory mice, rats and calves given. Content of trace elements in blood of calves in dynamics of the experiment was analyzed. There were determined parameters of acute toxicity of the analyzed preparations: they all could be referred to substance hazard category 4 (low-hazardous substances). The determined parameters of acute toxicity made it possible to recommend them for treatment and prophylaxis of microelementoses of cattle, as well as to use them as feed additives taking into consideration that defect action levels of the analysed preparations exceed the deficiency needs of cattle in case of their limited cumulation

Evaluation of safety and efficiency of application of immunostimulative drug Izambenum (C14H15IN2O) for stimulation of natural resistance (autarcesis) and immunologic responsiveness of chickens of laying breeds was realized in the conditions of the Republic of Belarus. Clinical and experimental investigation of Izambenum influence on poultry for the increasing of their resistance, activation of immunological response to vaccination against Newcastle disease, stimulation of their growth and development was realized. Research results showed that Izambenum influenced on level of morphological indexes of chicken blood: number of erythrocytes increased on 24%, hemoglobin - on 17%. Total protein in blood serum increased in all test period and number of lymphocytes increased and differential was 90-100%. Izambenum increased strains of post vaccination immunity to Newcastle disease. Bacterial growth-inhibitory activity decreased on the 27the day of life and increased at the same positions on the 34-41 days. Phagocyte activity of pseudoeosinophils increased in all test groups. Research results showed that Izambenum rendered growth and immunity stimulation action and increased their viability. Its immunostimulative action was conditioned by strengthening of cellular and to lower extent humoral immunity factors. Application of the preparation in period of Newcastle disease vaccination promoted the formation of long-lived immunity

Results of studies of acute and chronic toxicity of control samples of long acting boluses on the basis of fenbendazole for the treatment of strongylatosis (Strongylata) of gastro-intestinal tract of cattle realized in the conditions of the Republic of Belarus were presented. White rats and mice were used for studying of acute and chronic toxicity of the prolonged anthelmintic. The preparation was tested in doses of 400; 800; 1200; 1600; and 2000 mg/kg of body weight. Prolonged anthelmintic was administrated introgastrally in the form of suspension. Preparation was reduced to fragments before application. White rats with body weight of 80-100 g were divided in three groups and were used for testing. Bolus of prolonged activity was reduced to fragments and mixed with feed before application. Rats ate the preparation during 30 day in dozes of 250 mg/kg, 375 mg/kg, and 500 mg/kg. Study of acute toxicity of preparation established that LD0 for white mice was 400 mg/kg; LD16 - 620 mg/kg; LD50 - 1080 (1062,7 / 1097, 3) mg/kg; LD84 - 1660, LD100 - 200 mg/kg. Signs of animal toxicosis were revealed in shakiness, depression, whiteness of visually accessible mucous coat, cramps. Catarrhal-haemorrhagic gastroenteritis and numerous effusions of blood on mucous coat of digestive tract were established at postmortem examination. There were no morphological changes in tissues of lungs, heart, liver and nephros. Eating of prolonged anthelmintic with feed during 30 days did not render toxicological influence on rats. There were no signs of intoxication, physiological deviations and no animal death. Research results showed that the analyzed prolonged anthelmintic could be referred the substance hazard category 3