In the conditions of the Republic of Belarus there was studied rumen digestion of ruminants after their feeding with green mass of buckwheat (Fagopyrum esculentum) and buckwheat haylage. Special attention was given to studying of enzymatic processes taking place in rumen. The experiments were realized in vitro with application of simulator Rusinec (Rumirant Simulation Technique) for the imitation of digestion processes taking place in cattle rumen. On the Rusinec (n=4/diet) stimulator there were analyzed 5 rations on the basis of hay with buckwhear addition in dose of 0,300 or 600 g/kg on the form of green mass and haylage. None of the above mentioned forms of buckwheat in vitro experiments rendered negative influence on rumen digestion and concentration of volatile fatty acids. Application of buckwheat green mass made it possible to lower the quantity of bacterium in rumen content; while buckwheat haylage – the number of protozoon organisms. There was marked a tendency to lowering of fleshed methane.

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 were studied the productive and interior indexes of bull calves which were fed with dried distiller's grains. Inclusion into bull calves diets of the mixed fodder containing 33% of dried distiller's grains made it possible to increase the concentration of volatile fatty acids on 16-18%, albuminous nitrogen - on 4-7%, quantity of infusorians - on 16-17%, as well as to reduce the ammonia level in a ruminal liquid from 23,4 up to 17 mg%. Inclusion of 33% of dried distiller's grains into structure of mixed fodder and feeding the same quantity of fresh distiller's grains promoted increasing of nutrient digestibility on respectively 4,0-5,9% and 3,5-4,5%, nitrogen retention - on 13%. Increasing of level of dried distiller's grains in structure of grain forage up to 67% increased the digestibility of nutrients on 1,5-2% and nitrogen retention - on 4%. Substitution in mixed fodder for bull-calves of 33 and 67% of fodder grain by dried distiller's grains made it possible to increase daily average live weight gain of animals respectively on 10 and 4%. Feeding of dried and fresh distiller's grains at simultaneous introduction in rations of complex mineral additive promoted the activation of metabolic processes that was proved by increasing of crude protein of blood at 6-7% and 5-8%, as well as decreasing of concentration of urea - on 25 and 22% respectively. Use of 33% of dried distiller's grains as a part of mixed fodder for cattle young stock proved to be economically effective and allowed to lower the cost price of a live weight gain on 10-11%. Feeding with fresh distiller's grains allowed to lower the prime cost price on 7% and to receive additional profit.

In the conditions of the Republic of Belarus there was realized a comparative study of meat productivity of mongrel Gereford х black-and-white heifers ad purebred black-and-white heifers in the conditions of different levels of concentrated feedstuff in cattle diets; and determine the most efficient and long-term method of animal breeding for meat. Research results showed that breeding of meaty of hybrids of Gereford х black-and-white heifers of the second generation without using the feeding concentrates in their diets or on using rations with a low rate of feeding concentrates (10-20%) proved to be more effective, than breeding of purebred black-and-white herdmates (for which specific density of the concentrated forages in diets made up 20% through pregnancy). Hybrids on Gereford breed in accordance with meat productivity level surpassed the purebred black-and-white animals. The most considerable results were marked at hybrid heifers with relative density of concentrates in a ration of 20% which in accordance with slaughter weight indexes surpassed the herdmates of black-and-white breed on 39,1 kg or on 23,68%, in accordance with slaughter yield - on 8,2%, in accordance with fresh carcass weight - on 37,9 kg or on 23,8%, in accordance with weight of inner porc - on 1,19 kg or on 20,62%.

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 studied the influence of high degree of cow productivity on the course of down-lying and state of endocrine status of animals and their reproductive qualities. Application of veterinary preparations Katozal and Ovoton made it possible to control the functional activity of cow dam and ovary providing the increasing of cow reproduction qualities. Results of tests of estradiol-17 beta and progesterone in blood serum of experimental and control groups cows were presented. Application of Katozal and Ovoton veterinary drugs made it possible to cause heat and insemination of 86,5-91,3% of cows. At the same time, according to the results of the first insemination the highest results were obtained at cows with low productivity indexes – 60,9% and according to productivity increasing this index lowered up to 32,7% and 29,8%, respectively. According to the results of all insemination in cases of 3500-5000 kg productivity only 2 cows (8,7%) were nonbearing.

In the conditions of the Republic of Belarus there was studied the possibility of application of biotechnological methods of correction of sexual function of infertile cows and heifers (oestrus stimulation and synchronization) a dairy cattle breeding farms with high breeding productivity indexes and simultaneous metabolic function diseases. In course of the study there were applied clinical, cytodetection technique, haemotological, biochemical and analytical methods. Results of three-year studies of pathological metabolic disorders of cows (chronic acidosis; chronic ketoacidosis; dystrophic liver affection; renal irritation syndrome; disturbance of calcium and phosphorous ratio; trace element deficiencies; hypovitaminoses) were analyzed. Structure of obstetric-gynecologic pathology in experimental dairy cows herd was presented. Research results showed that high reproduction indexes of cows were the contributory cause for development of metabolic disorders. In such conditions for the efficient stock reproduction it was proposed to apply the mandatory hormonal stimulation of sexual function by means of application of the Ovsinkh scheme.

In the conditions of the Republic of Belarus there was studied the clinical and biochemical status of pregnant cows, as well as the determination of the main reasons of disease incidence of new-born calves with dyspepsia (dyspeptic disorder). Realized clinical and biochemical studies showed that the inappropriate feeding of pregnant cows in animal breeding farms in housing season of husbandry caused the disorders of metabolic processes in the experimental animals. In blood there was noted the lowering of indexes of alkalinity reserve, glucose, phosphorous, carotine, disturbance of calcareous and phosphorous ratio. In other words, in pregnant cows there were stated the latent forms of osteodystrophia, hypovitaminosis A, hypoglycemia, and acidosis. All these factors caused the irritation and damage of liver and other organs. Mammary gland of diseased animals released colostrum milk of low quality and according to the content of nutritious and protective elements quantity it was of low quantity. Besides, derangements in calf feeding of pregnant nonmilking cows led to birth of calves with low resistance indexes to the influence of external environment factors.

In the conditions of the Republic of Belarus there were analyzed the efficiency of application of a new mineral additive produced of the basis of carnallite brine (the national local raw material) as a part of mixed fodders for feeding of young stock of cattle. There was analyzed its influence on digestibility of a diet nutrients in cattle rations and on animal productivity. Inclusion of carnallite brine in mixed fodders structure for fattening young cattle rendered a positive influence on forage palatability. Forage consumption on a per head basis increased on 5,4%. Optimum dose of addition of carnallite brine in mixed fodder - 0,85%. Feeding of young cattle with the experimental mixed fodders did not render negative influence on hematological indices and physiological condition of animals. Use in young cattle rations of the mixed fodder containing 0,85% of carnallite brine promoted the increasing of nutrient digestibility on 3,4-5,7%. In the conditions of feeding of mixed fodders with other doses of carnallite did not cause any changes in digestibility of nutrients. Feeding of the prepared mixed fodder with 0,85% of carnallite brine to young growth of cattle made it possible to increase the growth energy on 5%.

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.