The efficacy of different doses and periods of feeding preparation of yeast origin NuPro (nucleoprotein) were studied in two scientific experiments on broiler chickens cross "Ross-308" in a production environment of Starosilska station LLC "Cherkassy Poultry Plant" (p. Staroselie, Gorodishche county, Cherkasy region, Ukraine). For both experiments (directly in the poultry house with a total capacity of 16 ths. birds) 500 broiler chickens were selected, and divided into 5 groups of 100 birds each. In the first experiment, starting from the first day, chicks of the first (control) group were fed with standard fully balanced feed. The poultry of 2, 3, 4 and 5th experimental groups were fed with the same feed, but during the first 7 days the feed was supplemented with 1, 2, 3, and 4 % of mass fraction of the preparation NuPro. In the second experiment, control broilers group received feed without preparationof NuPro. During respectively – 7, 14, 21 and 42 days the poultry of 2, 3, 4 and 5th experimental groups were fed with the same fodder, but with adding to it the optimal dose NuPro.

During the experiments feed intake, body weight dynamics and safety of livestock broiler chickens, feed conversion, microbiological, and hematological parameters slaughter were studied. The results were subjected to biometric processing.

Results of the 1st experiment showed that the introduction of NuPro into a feed in 1–4 % of mass fraction improved growth rate of experimental chickens. The average daily weight gain for the 1st week in control chickens was 21.7 g., at the same time their analogues in 2, 3, 4 and 5th research groups gained by 6.8; 8.7; 7.3 and 4.2% more. Body weight of broilers of 2-4th research groups at 42-day of age was also higher and amounted to 2622,8-2764,1 ageinst 2534.8 g in control, with a simultaneous reduction in feed costs by 1,1–2,2 %. The overall evaluation of the results of the 1st experiment established that the optimal dose of NuPro in the fodder is 20 kg/t. In the second experiment the supplementation of the feedstuff with the optimal dose NuPro during 7 days improved feed intake of broilers of experimental groups compared to the control, and increased average daily gain respectively: during the first week – by 12,0–12,9 %,during the second week – 10,8–13,6 % and 3rd week – by 9,8–14,5 % (P<0,05). For the growing period from 21 to 42 th day, when feedstuff with NuPro supplementation was fed only to birds of 5th experimental group, an average daily gain of chickens in all research groups prevailed control by 8,7–14,2 %. Overall, throughout the whole experiment an average daily gain of broilers in 2-5th experimental groups were higher than control by 9,2–13,7 %. Survival rate of chickens was the highest in 3 and 4 experimental groups – 99 %, and the cost of feed for poultry in the 2-5-th research groups decreased by 3,5–9,6 %.

Supplementation of NuPro to the fodder was accompanied by a decrease in broiler’s droppings of escherichia enterococci with a simultaneous increase of the desired flora – bifidobacteria and lactobacilli. The difference compared to the control, was, respectively – 7,9–17,0 and 6,6–15,5 % with NuPro feeding within 14 days, and 7,0–24,2 and 6,2–22,6 % with NuPro feeding for 21-day and 6,1–28,6 % and 4,9–27,0 % with NuPro feeding for 42-days (5th experimental group).

The results of blood tests revealed that the blood of birds in experimental groups had more red blood cells, higher hemoglobin, total protein, nucleic acids, and observed increased enzymatic activity.

Controlled slaughter demonstrated that the weight of broilers in the 2–5 th research groups exceeded control analogs by 187,6–265,6 g, slaughter body yield – by 0,87–1,42 %, processed chicken weight – by 141,9–206,4 g, or 10,4–15,1 %. The greatest difference between the indexes of processed broilers in the experimental and control groups took place when NuPro was fed during 14 th and 21 days (3rd and 4th experimental group) and continuously (fifth experimental group).

Meat quality of broiler from research groups dominated over control group. In particular: the total weight of the edible body parts of the broilers in the 2 nd experimental group was higher than the control by 6,1 % and by 18,3–19,5 % (P<0,001) in the 3-5th research groups, thoracic mass m ' muscles of broiler carcass 2-5 th experimental group was higher than in control, to 15,0–24,2 %, muscle mass of the thighs and legs – 10,9–17,4 and body, wings and neck – on 17,3–24,3 %. Utilization of NuPro supplement in feedstuff helped reduce amount of inedible body parts in experimental broilers compared to control by 4,2–5,8 %, which, in turn, improved their meat index (5,46–5,84 against 4,62 in control).

The overall evaluation of the data suggests that 42-, 21- and 14-days NuPro feeding periods provides the best impact on the growth of broiler chickens. Additionally, according to economic estimates, the optimal supplementation dose of feedstuff with NuPro (20 kg / t) over 7, 14 and 21 th day provides additional profits from each broiler at 2,26; 3,21 2,83 GRN in the corresponding groups, and the continuous feeding brings loss at 0.31 GRN per broiler.

Key words: broiler chickens, productivity, feeding period dozes.