INTRODUCTION Due to the peculiarities of their bottom, the Dnipro reservoirs were created in the form of a cascade 1. Taking into account human impact on natural and artificial reservoirs, their hydroecological state is constantly changing, there are changes of hydrology, water quality, hydrobiological characteristics, among which special attention should be paid to the ichthyocenosis. Among the Dnipro river reservoirs, the Kremenchuk and Kakhovka ones are marked by the largest areas of the water surface (225 and 215,5 thousand hectares), the largest filling of the water level during the year (4-6; 2-4 m), the maximum of which falls on the winter period (January-March), and the lowest complete water exchange (2,5-4; 2-3 times a year) 2. According to the location of the cascade of reservoirs from south to north, the Kakhovka reservoir is located in the lower flow of the Dnipro river in the steppe zone, lower than others which affects its hydrobiological features. The Kakhovka reservoir was filled with water in 1956, it has an open top that flows directly into the river and has the largest width at the top, which reaches almost 23 km. The area of shallow water with depths is 2 m and occupies 5%, where, mainly, vegetation grows and phytophilous fish spawn. The Kremenchuk reservoir is located on the middle flow of the Dnipro river in the forest-steppe zone of Ukraine. Its top is supported by a barrier above the Dnipro reservoir. Shallow water in the Kremenchuk reservoir makes up 18% of the total area. Filling of the Kremenchuk reservoir with water to the planning level lasted for two years, during 1960-1961. The Kremenchuk reservoir is distinguished by the presence of three large tributaries of the Sula, Vilshanka, and Ros 3 , a considerably larger area of shallow water with depths of up to 2 m, and a width of up to 30 km in the
Background: Dnipropetrovsk region of Ukraine is located in the northern steppe subzone, where livestock is actively developing, including dairy farming. Cows, imported from other ecological and climatic conditions undergo appropriate acclimatization to new conditions of exploitation. The current research was based on the assessment of the adaptive properties of Holstein cows of different ages to manage and control the level of their milk productivity and reproductive function during exploitation. Methods: All researches were carried out on the milk complex of “Agro-Soyuz”. The information base was data on productive qualities in individual cards of cows, results of assessment of zootechnical and veterinary accounting. To achieve this goal, an analysis was conducted from the first to the seventh lactation of Holstein cows. Result: Our researches allowed establishing the adaptability of Holstein cows of different ages in terms of ecological plasticity of the northern steppe of Ukraine. With a slight imbalance of the organism and the environment cows show high productive qualities at unsatisfactory reproductive function. This work will be a complementary the comprehensive study the adaptation of Holstein cows in different climatic conditions.
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