The purpose of the study is improving different body systems of animals in separate development phases of postnatal ontogenesis. To achieve this goal we studied the patterns of age-related changes of the activity of aspartate aminotransferase in the tissues of the duodenum of rabbits in different phases. Used rabbits breed gray giant at the age 1, 6, 12, 18, 24, 30, 45, 60, 90 and 120 days. The duodenum was divided into three parts: proximal, medial and distal. In every part of the duodenum was isolated two layers: mucous and muscle. In their studies of early postnatal life of rabbits was divided into phases. The studies show that due to changes in the structure and function of the muscular and mucous layers of the mucous membrane of the duodenum, due to changes in the composition and amount of food the activity of the enzyme varies. The activity of AST in the tissues of the mucous and muscle layers of the proximal, medial and distal parts of the duodenum at the age 1 day of rabbits in the colostrum nutrition phase, compared with other age groups, relatively low. In the first six days of life, in colostrum nutrition phase, the enzyme activity increases significantly. To twelve daily age rabbits, in the first dairy feeding phase, the activity of AST also increased significantly. Subsequently, the daily age of eighteen, in the second phase of dairy feeding, the activity of AST decreased significantly in the tissues of both layers ofthe proximal, medial and distal parts of the duodenum. Fromthedailyage of eighteen of rabbits in the tissues mucous layer of the proximal, medial and distal parts and in muscle layer of the distal part of the duodenum, the activity of AST is stabilized. In the muscle layer of the proximal and medial parts of the gut in subsequent phases of feeding rabbits the nature and intensity of age-related changes in activity of AST are slightly different. These distinctive features in the muscle layer of the mentioned parts of the duodenum, possibly associated with peculiarities of generation of their structure. Thus, the most intensive processes of transamination of aminoacids with the participation of aspartate aminotransferase in the examined tissues are seen in rabbits at early stages of postnatal period, toeighteendayold.

The purpose of the study is improvement of various in in animals body systems in separate development phases of postnatal ontogenesis. To achieve this goal, we have studied the regularities of age-related changes in the activity of gamma-glutamyl transferase in the tissues of the muscles biceps and triceps brachii, quadriceps femoris, gluteus and gastrocnemius muscles of the extremities in rabbits in different phases.Used gray giant breed rabbits at the age 1, 6, 12, 18, 24, 30, 45, 60, 90 and 120 days. Age groups were formed according to the principle of unique, taking into account gender, body weight, type of nervous system and general condition. The animal muscle tissue samples were removed and frozen in liquid nitrogen for further research. The activity of gamma glutamyl transferase was determined by photocolorimetric and spectrophotometric methods in the scientific laboratory of the Department of Agricultural Chemistry and Ecology of the Academy. The resalts show the nature of age-related changes of the enzyme levels in the tissues of the biceps and triceps the first forty-five days of life is about the same. But it should be noted that the increase or decrease intensity of GGT activity in the tissues during this lifetime differs. In the rest of the studied periods of life the nature of the activity of the enzyme in the biceps and shoulder triceps is different. The most intensive changes in the GGT level in the tissues of the biceps is detected from two-month to three-month age (increased 2.7 times, p<0.001) in the tissues of the triceps – from forty-five daily to two months (increased 3.9 times) and from three-months to four-months (increased 3.0 times, p<0.001). The character of changes of enzyme activity in the tissues of thigh quadriceps at different age rabbits differs from that of the rest of the studied muscles. The most intensive GGT activity changes from twenty-four to thirty days age (increased 4.0 times, p<0.001). Age-related changes in GGT level in the tissues of the gluteus and calf muscles are basically the same. The difference is found only in the first six days of rabbits` life. Enzyme level in rabbits in the tissues of the gluteus maximus during the first six days increased by 91.0%, p<0.05, and in the tissues of the calf muscle, it falls to 27.3%, p<0.05.