In the conditions of the Republic of Belarus there was studied the interrelation between content of major nutrient elements (calcium and phosphorous) and trace elements (iron, copper, cobalt, and manganese) in forages and blood of first-calf cows at the first and last stages of lactation. Also, there were developed formulas of mixed forages and a premix for these animals. The studies were realized at the Agricultural Production Co-operative Olgovskoe of Vitebsk region (Belarus). Research of analysis of forages and state of mineral metabolismat heifers made it possible to draw following conclusions: in cow rations there was marked the deficiency of vitamin D, as well as some trace elements (cobalt and manganese) in the conditions of calcium and phosphorus excess. In spite of a high content in a calcium in diets, it was noted than in blood plasma the concentration of this element was below the standard for the majority of animals. Lack of cobalt and manganese of whole blood of cows was connected with a low level of these elements in cow diets. The surplus contents of copper in forages and blood of animals against the background low activity of ceruloplasmin the weakened antioxidant defense of heifer cows. For preventive treatment of possible hypo trace element deficiencies and metabolic disorders of heifer cows at the final stage of lactation there can be recommended the correcting of cow diets with inclusion into their composition of the developed for compound of mixed fodder and premix.

Data on development of an antigen on the basis of larvae of warble flies grubs (Hypodenna bovis) for diagnostic of spontaneous cattle hypodermosis by means of the indirect fluorescent (IFA) test and with application of blood serum and milk samples realized in the conditions of the Republic of Belarus were presented. Specificity and sensitivity of experimental sample of antigen for revealing of spontaneously infestated with larvae of warble flies with IFA test at hypodermotosis has made about 100%.

Investigation of peculiar features of productive and reproductive qualities (milk producing ability; reproductive qualities; live weight at different ages) of milking cows of white-and-black breed was realized in the conditions of CJSC Lipovtsy of Vitebsk region of the Republic of Belarus. On the basis of obtained results there was calculated the selective differential of milk yield and butter-fat yielding capacity which were increased by means of maternal and father's cattle; genetic progress through selection in reliance on generation and target standard for the analyzed herd, as well as the minimal requirements to first-calf heifer productivity.Research results showed that average milk yield in the analyzed herd was 5204 kg with average butterfat percentage 3,59%; for first-calf heifers – 4838 kg with butter-fat yield of 3,47%. Productivity of first-calf heifers and cows was higher than the standard valuation requirements to milk yield on 1350-1588 kg

The given research results of feeding highly productive cows with new forage supplement of humic-melanoidine nature during the milking period show stable mineral metabolism, correction of their redundant supply within the diet, perfection of digestion and transition into milk as well as minimizing consequences of metabolism intensification. Reception new forage supplement promoted improvement of mastering by an animals organism of necessary iron during the given physiological period, to restriction of mastering of the microelements equal to the category of heavy metals

In the conditions of the Republic of Belarus there was studied the activity of hepatic specific enzymes of blood serum of bull calves of black-and-white breed in course of application of various doses of zinc-containing preparations. Application of zinc-containing preparations led to multidirectional change of activity of hepatic specific serum enzymes. Application of Zinkovet preparation in dose of 1,8 g/100 kg of live weight made it possible to essentially grade the indexes of hepatic tissue affect. In the experimental group at animals there was marked the lowering in activity alanine-aminotransferase, serum glutamic oxalacetic transaminase and gamma-glutamyl transpeptidase. At the same time, there was noted the increasing of zinc-containing enzymes activity (sorbitol dehydrogenase and glutamate dehydrogenase). All these processes were caused by zinc inclusion into the metabolic process.

In the conditions of the Republic of Belarus there was studied the nonspecific resistance of lambs of Latvian Black Face breed during the colostrum and milk fed period of their growth development. In course of the experiment there were used 10 newborn lambs. Analysis of resistance was realized in accordance with a scheme: before colostral milk sucking; in 6, 12, 24 hours; in 3, 7, 14, 21 days; in 1, 2 and 3 months after birth. In lambs during the colostrum and milk fed period of growth there were marked two critical periods, which were characterized by low indicators of resistance: before colostral milk uptake and at 7-21 day-old age. Increasing of leukocytes, bactericidal, lysozymic activity of blood serum, phagocytal activity of leukocytes, crude protein and antibodies in the first days of lamb life took place due to their entrance in blood with colostral milk, just because at this time the intestines wall possessed ability to transit in native condition the antibodies, enzymes, and leukocytes. At 7-21 day-old age in connection with reduction of these factors quantity of in colostral milk, and also due to reduction of intestines capacity, their was stated that their entrance in blood of newborn lambs decreased, but at 3 month old age of lambs there were stated to form internal protective factors of resistance because of which their quantity in blood started to increase.

In the conditions of the Republic of Belarus there was realized a comparative study of peculiar features of influence of combined application of Khelavit preparation and protein-vitamin-mineral feed supplements Khendriks and Spaeta-kontsentrat on health status of cows and quality of obtained cow milk after application of these preparation for the preventive treatment of osteodystrophy. In course of study there were analyzed haematologic and biochemical blood indexes of cows after application of the experimental preparations. Results of physical and chemical indexes of milk were presented. Research results showed that the analyzed protein, vitamin and mineral feed supplements caused the normalization of biochemical blood indexes in comparison with animal of a control group. Besides, application of mentioned above drugs promoted the increasing of veterinary and sanitary quality and technological properties of produced milk.

In the conditions of the Republic of Belarus there was analyzed the interrelation between the main indexes of cattle milk performance of dairy cattle of Large Red Belarusian breed and Belarusian Black-and-White breed with different genotypes of kappa casein gene. In course of the study there was determined the frequency of occurrence of genotypes and alleles by kappa-casein gene in population of cows of mentioned above breeds. Values of correlation coefficients between some indexes of milk performance of the studied breeds were analyzed. Correlation factors between the basic indexes of milk performance of cows with different genotypes of kappa casein. Research results showed that milk protein content and butter-fat yielding capacity were in negative association with the main breeding trait of dairy cattle – amount of milk yield. Butter-fat yielding capacity and milk protein content correlated positively. Thus, selection breeding in accordance with one of this traits will promote increasing of the other. Besides, it is necessary to realize DNA-diagnostics of cattle according to kappa casein gene and to select animals having in their genomes allele CSN3**B connected with higher milk protein content.

Factors which increased milk productivity (age and continuance of service period) were studied in the conditions of an educational establishment of the Republic of Belarus by an example of cows of black-and-white breed. Dynamics of growth of milk productivity in course of 8 research years was presented. Analysis of interrelation between cow productivity and cow age was given. Mathematical calculation of relations between cow productivity indexes (milk yield, fat content, butter fat) and service period duration was given. Research results showed that increasing of an average term of economic use of cows and decreasing of duration of service period up to 90 days made it possible to increase dairy effiiemcy and herd reproduction, as well as obtain higher economic efficiency

Results of the scientifically-economic experience lead in farm Zarechje (Smolevichskij district of the Minsk area) have shown, that perfect metabolizable energy concentration in dry matter of a diet at milking period for first-calve cows is 11,7 MJ/kg. It allows to increase natural milk productivity at 8,24% (27,4 against 25,4 kg) and 4%-milk outcome – at 8,93% as well as effective usage of metabolizable energy for production up to 4,9% (P less than 0,01) and minimum of production warmth loses