This article gives results of research of the impact of ptebiotic preparations Laktobas and Probifid on microflora of the digestive tract of a boiler chickens. The correction of microflora of poultry was installed to upward a normal flora and to reduce pathogenic microflora. Strains that been used in biotechnology of probiotics characterized by an unique combination of a hight antagonistic action to pathogens,hight immunomodulatory, metabolic activity, harmlessness for macroorganism and automicroflora, hight resistance to the external environment. A health of poultry depends of a balance between normal and potentionally pathogenic microflora. Any changes in this balance will be accompined with functional disorders wich, in turn, lead to lower productivity. Disbalance of intestine and death of chickens can be avoided by using probiotics. Receiving groups of new biotech drugs – immunobiotics – based on a pre-selected and characterized representatives of nomal microflora of poultry, including strains of lacto- and bifidobacteria – this is an important problem of modern biotechnology because of wide-using of this prebiotics, and prebiotic therapy is getting more popular than antimicrobial. That`s why development of probiotics and their using to prevent and cure diseases of livestock and poultry is an urgent task today. Disfunction of the immune system resulting from a changes in the environment, wide application of new chematotherapeutic agents of different nature, disruption of normal microflora is one of the major causes of icreasing aggresivness of opportunistic commensal microorganisms with subsequent development of infectious and inflammatory disease. The results of experimental studies, that have been obtained in recent years, show that under influence of the probiotics was observed a normal flora of alimentary canal, immune status – was restored; increased phagocitic activity of monocytes, neutrophils and macrophags.

Strains that been used in biotechnology of a probiotics are characterized by an unique stats: combination of high antagonistic action to pathogens, high immunomodulatory, metabolic activity, non-harming to the microorganism and automicroflora, high resistance to environmental conditions.

Modern requirements of the European regulatory law in the field of probiotics include the need for comprehensive studies of the biological activity of individual probiotic cultures, and combinations of them, when creating products based on probiotic monocultures lacto- and bifidobacteria or their different combinations. The aim was to study the influence of probiotic preparations Laktokas and Probifid on the composition of intestinal microflora of a broiler-chickens.

Experimental studies were performed in a vivarium conditions of the BNAU. The experiment was carried out on the groups-analogues of broiler-chickens of a cross: «Cobb-500», that was formed in the 2 groups. Preparations used with food, throughout all of the growing period: the second group received probiotic «Laktokas» and «Probifid» in a dose of 0,5 g/kg and the first group of a poultry served as controls and received a standard diet. For the researches were used: a drugs Laktokas (dry form) and Probifid – probiotic supplements for poultry, composed of a lyophilized strains Lactobacillus casei ІМВ В-7280 and Bifidobacterium animalis VKB. Chickens of all groups were kept indoors with floor maintenance system in compliance of all zoohygienic requirements. Microflora of the intestinal tract of birds were tested, by seeding bacterial trials on the selective medium. Isolation and identification of microorganisms was performed by using a multistage system, which included the allocation of a pure culture, learning their cultural, morphological, tinturial and biochemical properties of these cultures. For the microbiological studies there were used: selected samples of the containance in different parts of the intestine tract of a chickens. In 1 g of the containence of the guts was determined number of E. coli, lactobacteria and bifidobacteria. There were conducted a calculations of the quantitative composition of the studied bacteria samples, the results were transferred into a logarithms to define a ratio of a different groups of microorganisms of the microbiocenosis in the intestines of a chickens in a different age groups. With using studied drugs, was found, that correction of the intestinal microflora of the poultry was holding upwards beneficial microorganisms and reducing the pathogenic microflora. This studies tell us that, it is advisable to use drugs: Laktokas and Probifid to normalize microflora of the animals, especially in industrial poultry-keeping. Those are an ecologically pure drugs that are physiological and safety for poultry. Further researches should be aimed at the studying of the action of probiotics on the resulting quality of poultry’s products.

Key words: probiotic preparations, immunomodulated properties, probiotic strains, gut, lactobacteriae, bifidobacteria, broiler chickens, microorganism.