During the panic, hens of white egg crosses, which are generally characterized by excessive timidity, immediately resort to escape and hysterically fight against the partitions and other elements that enclose the territory of their stay. It leads to numerous injuries, bleeding in the liver and ovaries, peritonitis, mass physiological anovulations and other disorders of the ovulatory cycles, and thus -at overcrowding, ie at 26 and 28 hens/m2, respe to reduction or stop of egg production and even death. Therefore, it is the level of egg production that determines and evaluates the reaction of the body of hens to acute stress in the first place, also for the immediate elimination of its stimulus. With regard to chronic stress, its diagnosis is complicated by the subtle current effects on the body of laying hens. However, with prolonged and cumulative action of the stimulus, it also causes significant material losses. The lack of a significant number of eggs under uncomfortable conditions of keeping hens during the year is probably a consequence of their being in a state of chronic stress. However, the possibility and effectiveness of its detection by the level of laying hens, especially at the beginning of the stimulus, has not been studied yet. This is especially true of situations that arise when the density of laying hens in cages. The urgency of detecting chronic stressors by the egg laying capacity of hens is also connected with the lack of objective data on the amount of material losses during their operation. Due to it and the attempt to obtain as many food eggs as possible from 1 m2 of available technological areas, some of their powerful producers resort to keeping the laying hens in the cages of multitiered batteries and even at higher densities, ie not at the densities recommended by the developer of the cross, but at higher ones established by the domestic standards. Therefore, the aim of the experiment was to determine the response of the reproductive system of hens to the intensity of chronic stressors formed by keeping them in cages of 12-tier batteries at a slightly higher density. To do it, on the conditions of a modern complex of the alimentary egg production 3 groups of laying hens of industrial herd of the cross «Hy-Line W-36» were formed, each was kept in a separate poultry house-analogue (area 2463.3 m2) with 12-tier cages batteries «Salmet», consisting of 30912 cages with the area of 0.392 m2. Hens of the 1st (control) group were kept at a density of 23 hens/m2 in accordance with domestic standards, and the 2nd and 3rd groups – at overcrowding, ie at 26 and 28 hens/m2, respectively. The effect of chronic stress on hens was determined by standard zootechnic and morphological methods of measuring their egg production, preservation, live weight and weight of eggs, strength and thickness of the shell, intensity of yolk color, etc. It was found that in accordance with the domestic requirements the normative density of keeping (23 hens/m2) of the hens of the cross «Hy-Line W-36» does not provide their inherent productivity, which should be at least 262.2 eggs per initial laying hen within 62 weeks of life (and at the density of keeping in the range of 13–20 hens/m2). In particular, in hens of group 1 it was (231.4 eggs/hen), ie it was 11.7% lower. Preservation of hens of group 1 (91.3%) also did not reach the normative level (96.4%). The increase in the intensity of chronic stressors, namely the increase in the density of hens of groups 2 and 3 to 26–28 hens/m2, led to a corresponding reaction of their body, in particular, to a decrease in egg productivity (up to 220.8–227.2 pcs/hen.) and preservation (up to 88.4–91.1%). This increase in the density of laying hens in the cages of 12-tier batteries to 26–28 hens/m2 (by 4–27% relative to domestic standards) provides for obtaining of 1.6–5.2 thousand more eggs from 1 m2 of poultry area, but under conditions of reduction of the level of the European coefficient of efficiency of their production. Thus, it was found that overcrowding of hens of the industrial flock of egg cross «Hy-Line W-36» is a chronic stressor, which causes a decrease not only in egg production due to ovulatory cycles, but also their viability and efficiency of egg production in general.

According to the current norms (DSTD-AIC-04.05.) the density of keeping chickens in cages should be 22–25 hens/m2, which corresponds to their provision with an area in the range of 400–450 cm2/hen. This level of housing density does not coincide with the slightly more comfortable (13–20 hens/m2, or 490–750 cm2/hen) established in the United States and EU countries for chickens of modern egg crosses (Council Directive 1999/74/EC). Therefore, it is important to study the egg productivity of chickens of industrial flocks in 6–15-tier cages batteries at a density in accordance with domestic and European standards. In the conditions of the modern industrial poultry complex in a comparative aspect two variants of the maintenance of laying hens in cages of 12-tier batteries are investigated. The first variant of keeping provided laying of laying hens in cages according to the European norms – 14 hens/m2 (726 cm2/hen), and the second – 25 hens/m2 (402 cm2/hen) that corresponded to domestic norms. It was found that the maintenance of laying hens of modern high-performance cross for 44 weeks (until reaching 62 weeks of age) in cages of 12-tier batteries in density in accordance with the requirements of domestic standards (22–25 hens/m2, or 400–450 cm2/hen) provides 32265 edible eggs (2023 kg of egg mass) from 1 m2 of poultry area, which is 1.8 times more than the density required by European standards (13–20 hens/m2, or 490–750 cm2/hen). In addition, 85.2 million eggs were obtained from hens kept in 12-tiered cage batteries of a poultry house with an area of 2640 m2 in terms of density in accordance with domestic norms that is 37.6 million eggs more than from their counterparts, retained by European standards. It has been proved that the density of keeping industrial chickens in cages of 1–3-tier batteries provided by domestic norms should be extended to the batteries of new 12-tier structures.

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