The results of the experiment on the use of protein-vitamin flour from wheat bran, divided into fractions with particle size of 140, 400 and 800 µm in the diet of domesticated quails are presented. The experiment lasted for 60 days and was carried out according to the generally accepted methods on quails of the Japanese breed, formed in four similar groups (one control and three experimental), 80 heads each, at the age of one-day old. All groups received compound feed (the main diet), prepared taking into account the age and physiological characteristics of quails, but in the bird diet of the 1st, 2nd and 3rd experimental groups, part of the wheat (7%) was replaced with wheat protein-vitamin flour of three fractions with a particle size of 140, 400 and 800 µm, respectively. The poultry was kept in a battery cage under required microclimate conditions. The effect of feeding fractionated protein-vitamin flour from wheat bran was studied on the survival rate of quail chicks, their growth rate, indicators of meat productivity and hematological parameters, changes in the species composition of microorganisms of the gastrointestinal tract. The optimal fractions of wheat bran flour as the new feed in the diets of quails were determined in terms of efficiency of their productive and physiological action. The introduction of protein-vitamin flour from wheat bran into the compound feed of quails with a particle size of 140 and 400 µm in the amount of 7% of the grain part of the diet increased the survival rate of quail chicks by 3.0%, the average daily gain in live weight by 2.30 and 5.59%, the weight of eviscerated bird carcass by 4.5 and 6.16%, protein content in meat by 0.84 and 0.57%. Feeding the quails with flour of various fractions did not have a positive effect on the conversion of feed into produce. The biochemical parameters of the quail chicks’ blood remained within the physiological norm. Fractionated protein-vitamin flour with a particle size of 400 and 800 µm stimulated the growth of bifidobacteria, and with a particle size of 140 and 800 µm inhibited the development of Escherichia coli.