LEBEDEVA2 Federal Agency of Scientific Organizations, 55a, Moskovskoe sh., St. Petersburg—Pushkin, 196601 Russia, e-mail leib1406@yandex.ru, shapievism@bk.ru; 2 Dubrovitsy, Podol’sk Region, Moscow Province, 142132 Russia, e-mail irledv@mail.ru Abstract Metabolic processes in milk-producing cows are substantially modified that is the main reason of different abnormalities in the reproductive function. <...> At the same time the pattern of metabolic changes and its influence on the reproductive capacity in high-producing dairy goats ( ) are yet unknown. <...> The aim of the present work was to study the activity of metabolic enzymes in the blood of Saanen goats depending on the period of the reproductive cycle and the competence for pregnancy maintenance. <...> We analyzed for the first time alterations in the serum activity of enzymes, regulating the intensity of protein-carbohydrate and energy metabolism including integration of metabolic processes, at different stages of goat gestation as well as prior to the mating period in animals with the negative outcome of the subsequent pregnancy. <...> The enzyme status of animals was assessed during the pre-mating period, the first half of pregnancy (1.5-2.5 months), and the second half of pregnancy (3.5-4.0 months). <...> Goats were divided into two groups — with the completed reproductive cycle (the birth of viable offspring, rupted reproductive cycle (abortions in the second half of pregnancy, = 15) and with the inter= 6). <...> Samples of blood serum were tested to determine concentrations of total protein and activities of several enzymes: aspartate aminotransferase (AST, EC 2.6.1.1), alanine aminotransferase (ALT, EC 2.6.1.2 ), gamma glutamyltransferase (GGT, EC 2.3.2.2), creatine phosphokinase (CPK, EC 2.7.3.2), alkaline phosphatase (ALP, EC 3.1.3.1), lactate dehydrogenase (LDH, EC 1.1.1.27), and alpha hydroxybutyrate dehydrogenase (isoenzymes of LDH: LDH-1 and LDH-2). <...> In goats with the completed reproductive cycle, the blood activity of AST in the second half of pregnancy was found to be 1.2 times lower (p < 0.05) than during the pre-mating period or the first half of pregnancy. <...> The activity of ALT in the blood serum of the animals increased 1.3 times (p < 0.01) by 1.5-2.5 months of pregnancy as compared with the pre-mating period and then decreased 1.9 times (p < 0.001) by 3.5-4.0 months of pregnancy. <...> The results of this research suggest a reduction in the intensity of some metabolic processes <...>