Ducks take the second place after chickens in the balance of meat production in Ukraine. The specific portion of duck meat production is about 13–15 %. Recently, The share has been rising and may reach 20 %. Ducks are high in fertility - a duck can yield as much as 100–140 ducklings, high growth rate – their body weight increases by 50–60 times in 7 weeks, high viability – they maintain their activity under reduced heating and feeding conditions, ducks have better ability to digest cellulose and a protein than chicken do which allows the use of high-fiber and unconventional feed that grow in the pools.

In this regard, breeding ducks can improve and diversify the meat balance in the meat market. However, the intensive use of new high-yielding breeds and duck crosses requires clarification of feeding standards based on profound study of carbohydrate, protein, lipid and mineral metabolism.

In order to ensure a high intensity of metabolic processes in the duck body, special attention should be paid to the digestion features. The hydrolysis of nutrients in the gastrointestinal tract are known to be closely related to its physiological state, which affects the  productivity.

Therefore, finding out the ontogenetic characteristics of digestive processes in the body of ducks can provide increase in the transformation of nutrients and biologically active substances of feed into the products. In this regard, our research aimed to study the age and organ-tissue features of protein metabolism and the intensity of digestive enzymes in ducks.

To achieve the aim, a herd of the Beijing broiler duck of STAP 53 (heavy) cross bred by French firm GRIMAUD FRERES SELECTION in the amount of 2 thousand heads was formed and studied in the conditions of the "Agrofirma Piski" of Mykolaiv district of Lviv region. The poultry was farmed on the floor with free access to feed and water. All the birds received full-fodder feed (PC), balanced for all nutrients and biologically active substances, according to the direction of production and the period of cultivation. The material for biochemical studies was taken during slaughter in ducks 1–6 days (adaptation and full use of yolk), 75-days (juvenile molten) and 180-day-old age (puberty, beginning of oviposition). During the experiment, the poultry productivity was controlled (growth, development and the beginning of oviposition). The experiment lasted for 6 months.

The liver, duodenal and pancreas tissue taken from 5–7 slaughtered ducks at the end of each age period and the concentration of soluble proteins by the Lowry method was determined along with proteolytic, amylolytic and lipolytic intensity.

An analysis of growth control results suggests that body weight was gradually increasing over the entire period of cultivation. However, the highest intensity of growth was observed up to 35 daytime age. From the 35th day of age, the average daily increments gradually decrease to 56 daily hours. According to the feeding technology, ducklings were fed the same diet until 14 day-old, and the composition of the diet changed since the third week, which obviously resulted ina decrease in average daily weight increase

Thus, it is necessary to increase the quantity and quality of nutrients and biologically active substances, in this critical period (change in the composition of the diet) associated with intense growth of feathers, in order to maintain the intensity of biosynthetic processes.

The average value of daily weight increase is directly related to the intensity of nutrients and biologically active substances, which is, in turn, closely related to the internsity of hydrolytic enzymes of the mucous membrane of the glandular stomach and duodenum.

Thus, proteolytic intensity was higher in 37-day ducks, compared to 6-day-olds by 14.57 %. In the period of high intensity of metabolic processes, a significant amount of energy that the body can provide at the expense of carbohydrates and lipids is required. The figure data show that amylolytic and lipolytic intensity in the gastric mucosa is reduced in the 37-day age birds. However, it increases in the duodenum and pancreas content in 37 days old ducks, respectively, by 15.29 and 5.88 %, providing an intensive digestion of lipids into fatty acids and their use in energy synthesis processes. According to some data, carbohydrates are a more affordable source of energy than lipids, but lipids can provide this process under carbohydrates deficiency.

Therefore, in order to level the change in the direction of synthetic processes in the ducklings organism during the critical period, namely from 14 to 28 days, it is necessary to add available carbohydrate and protein components to the diet in order to provide the synthesis processes  related to body weight increase and with intensive growth of the feathers mass, or to add biologically active feed additives, which increase the use of protein and energy exchange from the ingredients available in the diet.

Key words: broiler duckling, proteinase internsity, amylase internsity, lipase internsity, body weight, liver, duodenum mucous membrane, duodenum chyme, pancreas, glandular mucosa.