Methods available for measurement of plasma lipoprotein-cholesterol concentrations and activities of lipoprotein lipase, hepatic lipase, lecithin:cholesterol acyl transferase (LCAT), and cholesteryl ester transfer protein were adapted for use in cats. A combined ultracentrifugation/precipitation procedure was used to isolate very low-density lipoproteins (VLDL), then to separate low-density lipoproteins (LDL) from high-density lipoproteins (HDL). The reagent used, 92 mM heparin-manganese chloride, provided complete precipitation of LDL with only trace and insignificant contamination by HDL. Efforts to selectively measure lipoprotein lipase activity in plasma, collected after IV injection of heparin, by inhibiting hepatic lipase with sodium dodecyl sulfate were unsuccessful, and the activity of this enzyme was calculated as the difference between total and hepatic lipase activities. The latter was measured in the presence of high salt concentration to inhibit lipoprotein lipase. Cholesterol esterifying activity was identified in feline plasma and was typical of LCAT, in that it was dependent on apolipoprotein A-I as a cofactor. The intra-assay and interassay coefficients of variation for measurement of lipoprotein lipase, hepatic lipase, and LCAT activities were 18.4, 4.6, and 7.2%, and 20.4, 10.7, and 5.3%, respectively. Appreciable cholesteryl ester transfer protein activity was not detected in either undiluted or diluted plasma. These methods were subsequently used to investigate the effects of pregnancy and lactation on lipoprotein metabolism in a group of 10 queens. Plasma concentrations of cholesterol and triglycerides were unaltered during pregnancy, but the concentrations of VLDL-cholesterol increased and those of HDL-cholesterol decreased. During lactation, the concentrations of cholesterol and triglycerides decreased owing to reductions in VLDL-cholesterol and LDL-cholesterol concentrations and continued suppression of HDL-cholesterol. These changes were associated with alterations in the activities of lipoprotein lipase, which increased after parturition, and hepatic lipase, which increased during pregnancy and lactation, that may help explain their metabolic origins. The activity of LCAT remained unchanged.

In the conditions of the Republic of Belarus there was studied the preventive efficiency of various forms of a complex additive Felutsen against polymicroelementoses of calf-bearing dry cows and its influence on some of biochemical blood indexes. Research results proved high prophylactic efficacy of various forms of the additive Felutsen against polyhypomicroelementoses of calf-bearing dry cows. Restoration of a microelement homeostasis of cows made it possible to normalize the functional activity of liver, to prevent development renal insufficiency and dystrophic changes in bone tissue. The most expressed metabolic changes in blood of calf-bearing dry cows were stated after application of the carbohydrate-mineral additive Felutsen-briquette universal. There was given the analysis of structure of studied forms of complex additive Felutsen; indexes of trace element metabolism in cows; indexes of protein metabolism and level of nonprotein nitrogen; indexes of blood characterizing the functional condition of liver and carbohydrate metabolism of cows; indexes of trace element metabolism in cows after the termination of application of the additive.

Study of peculiar features of protein metabolism of healthy colts in the first three months of life was realized in the conditions of the Republic of Belarus. Research results showed that there was a tendency of increasing of hemoglobin concentration up to 150,270+/- 4,73 g/l, number of total protein of blood serum – up to 60,33 +/- 1,33 g/l, and the decreasing of uric acid up to 97,33 +/- 10,72 micromole /l. Quantity of beta-1 and alpha globulin fractions of serum protein fluctuated a little – from 10,78 +/- 3,69% up to 8,44 +/- 1,24% and from 25,12 +/- 4,84% up to 22,06 +/- 4,93%, respectively. The most essential changes of protein metabolism were stated at two month old colts, which had urea concentration of 5,25 +/- 0,23 micromole/l, alanine aminotransferase activity – 66,92 +/- 3,16 units/l, creatine content increased up to 77,37 +/- 5,83 micromole /l; and there was the lowering of aspartate transaminase level up t159,5 +/- 8,1units/l. There was stated the lowering of albumin quantity up to 32,07 +/- 2,19%, and increasing of alpha-1, alpha2- and beta2- globulin fractions up to 7,52 +/- 1,23%, 14,98 +/- 1,41%, 11,82 +/- 1,04%, respectively. At the age of three months the quantity of urea and creatinine in blood serum of colts remained at the same level, alanine aminotransferase activity decreased on 21,56%, and aspartate transaminase increased up to 204,33 +/- 10,37 units/l. At this period the quantity of albumin fractions was 44,56 +/- 6,59%., concentration of alpha-1, alpha2- and beta2- globulins decreased on 10,64%, 30,04% and 34,52%, respectively

Nowadays in connection with an interdiction for antibiotics use in animal feeding it is very actual to work out and apply new forms of probiotic preparations which should be as ecologically safe and harmless both to people and animal products. Probiotics make it possible to improve the digestibility of nutritive substances of forages, normalize metabolism, enrich with biologically active substances that promotes the increasing of their productivity. In the Republic of Belarus the probiotics are produced in the obviously insufficient quantity that creates problems of young stock livability. Influence of application of Akozil and Sublicin probiotics in diets of suckling calves on biochemical parameters of blood serum was analysed. It was stated that use of the analysed probiotics made it possible to decrease the level of urea and total cholesterol, to increase of the total protein content in blood serum of the experimental calves. There was noted the increasing of glucose level in blood serum of calves fed with Akozil. There was marked the tendency of more optimal level of calcium and phosphorus in calves having Sublicin in their diets. The obtained results testified the normalization of metabolic processes taking place in calves which were fed by the mentioned above probiotics

Influence of monocalcium phosphate on natural resistance and clinical indexes of blood of breeding bull calves of white-and-black breed was realized in the conditions of the Republic of Belarus. Bull calves of the first (control) group in the composition of their main ration were fed with mixed fodder K-66-b, hay, green mass and as a balanced phosphoric-potassium additive they were fed with8 grams of defluorinated phosphate per 1 kg of mixed feed. Bulls of the second, third and fourth experimental groups in combination with the standard ration instead of difluoridated phosphate were fed with 5; 10; and 15 grams monocalcium phosphate per 1 kg of combined feed, respectively. Research results showed that application of fodder monocalcium phosphate in addition to the main ration made it possible to increase calcium and phosphorus content in blood of experimental bull calves. In the control group phosphorous content was 2,17 micromole, in the experimental groups – 2,40-2,78 micromole; calcium content – 2,50 and 2,58-2,88 micromole, respectively. The analyzed additive rendered positive effect on protein exchange, increased the natural resistance, bacterial growth-inhibitory activity in blood serum in the third, fourth and second groups on 50,3%, 42,5%, and 40,3%, respectively; lysozyme activity – on 46,0%, 39,2%, and 32,3%, respectively; phagocytic activity of leukocytes – on 21,9%, 25%, and 19,1%