The study has stated that heifer replacements, from the date of birth to 18 months, got through transplantation of frozen-defrosted embryos were not inferior to and in many cases superior to the heifers of their age but got through traditional reproduction. Transplant first-calf heifers have a high level of milk productivity which amounts to 7536,10 kilos, with 3,62% of fat and 3,23% of protein. Thus they provide a good selection material for new generation champions to be chosen among them and for being used as mothers of bulls for service

The necessity of creation of the optimal conditions for production of high-quality dairy products was conditional upon the fact that milk is very unstable by its chemical and physical indicators biological liquid. There is no point in improving milk quality after the realized production. Results of the realized in the conditions of the Republic of Belarus evaluation of milk according to the sanitary and hygienic indices for the further improvement of its quality were presented. According to the data on milk purchasing it noted that in Belarus there was stated a noticeable reduction of milk quality in accordance with its grade of quality. Throughout the last years the relative density of realization of the premium quality milk was less than 50% (46,5% - in 2005, 48% - in 2006), and at the same time, the volume of sales of the second second-rate quality milk reduced on 7,6%, and volume of off-grade milk - on 0,7%. Milk quality at the studied in course of investigation dairy farms in the majority of cases was conditional upon such indicators as base-titratable acidity, bacterial number and quantity of somatic cells in milk. Titrate acidity indices in over than 36% of milk does not correspond in to standards of the Republic of Belarus. Evaluation of bacterial number in the produced milk showed that its main production volume (65,2%) corresponded to the first and second grades and 6,7% were off-grade quality. Somatic cells content in the studied milk samples in 27% corresponded to the extra fine grade, and only about 2% of the analysed milk samples corresponded to off-grade milk

In the conditions of the Republic of Belarus there was studied the efficiency of application of national mineral additives (mineral feed additive produced on the basis of dolomitic meal) in rations of milking cows. In course of the study there were analyzed physical and chemical blood indexes; hematological indexes of cows; biochemical blood indexes; mineral composition of blood; natural resistance of cows. As a result of the realized study it was established, that an optimum dose of a dolomitic meal for milking cows during the winter period was 0,3% per dry matter of a diet. There was proved the possibility of increasing of a daily average milk yield of cows on 11,7%, fat and protein content in milk - on 0,04 - 0,06%, as well as lowering of quantity of somatic cells on 13,6%. Application of a national mineral additive rendered the positive influence on blood indices to what that was proved by increasing of erythrocytes (on 10,9%), thrombocytes (on 5,4%), haemoglobin (on 6,5%), crude protein (on 10,6%), and also macro- and trace elements. Introduction of a dolomitic meal into cow diets made it possible to increase the indices of natural resistance of cows on 0,5 - 4,0%.

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.

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

Results of estimation of the real possibilities of milk production of extra fine grade in the conditions of the Republican unitary enterprise Educational Farm of Belarus State Academy of Agriculture in Mogilev region (Republic of Belarus) were presented. It was established, that carrying out of some organizational and technological actions for decreasing the level of somatic cells in milk made it possible to lower the level of somatic cells in finished products from 494,72 thousand per cube cm up to 289,15 thousand per cube cm. The obtained data corresponded to requirements of the Standard of the Republic of Belarus (STB 1598 - 2006 Cow milk. Requirements at purchases to the grade milk Extra). The realized experiment was developed on the basis of analytical model of cow commercial herd, constructed on the basis of the analysis of results of evaluation of quality of individual tests. Sales level of extra fine grade milk at the dairy commodity complex Parsino (Republic of Belarus) was 90,6%