The research objective was the definition of biologi- cal effect of probiotic of "Provagen" and Laktusan prebi- otic on meat efficiency and the quality of meat of broilers of cross-country of Ross 308 in the conditions of JSC AF Priazovskaya of Kagalnitsky area, Rostov Region from 2014 to 2016. The method of analogs created three experimental groups and one control, 1000 heads in each. All experimental chickens during the experi- ment received the main diet applied on poultry farm. The chickens of the 1st experimental group in addition to the main diet together with drinking water were given a probiotic of "Provagen" from the 1st to the 10th day of life in a dose of 0.0002 g/g, from the 11th to the 21st day of experiment - 0.0005 g/g; to a bird of the 2nd ex- perimental group - Lactusan prebiotic at the rate of 5 ml/g within the first three weeks of growth; the broilers of the 3rd experimental group at the same time of "Provagen" and "Lactusan" were given in similar dosag- es. For the assessment of the influence of studied prep- arations on the organism of chickens such indicators as dynamics of live weight, lethal qualities of broilers, mor- phological structure of carcasses and chemical compo- sition, nutritional and power value of meat were studied. The preparations positively influence the live mass of broilers, and also morphological structure of birds’ car- casses. Using biologically active agents in a complex allowed raising slaughter-out percentage of gutted car- casses of chickens to 0.8 %, an exit of production of the first category to 4 %, the content of muscular tissue in carcasses of birds for 1.19 % in comparison with control group. The most effective is combined use of prepara- tions.