Increased planting density refers to stress factors and has a negative impact on the physiological state and productivity of broiler chickens. The aim of the work was to study the effect of technological stress on the activity of key digestive hydrolases – pancreatic amylase and lipase in the chyme of the small intestine and blood serum in broiler chickens of the Smena-9 cross. For the experiment, control and experimental groups with planting densities of 20 and 30 kg/m2, respectively, were formed. On the 42nd day of cultivation, blood and chyme samples were taken from various parts of the gastrointestinal tract. It is proved that under stress conditions there is a decrease in the activity of both hydrolases. The most pronounced and stable changes were recorded for lipase. Lipase activity in duodenal and jejunal chyme, as well as in blood serum, significantly decreased (p <0.05) in the experimental group compared with the control group. A downward trend was found for pancreatic amylase, but no statistically significant differences were found in most of the studied locations. Based on the data obtained on the dynamics of hydrolases, as well as the calculation of the hydrolase index, it can be concluded that high-density stress negatively affects the secretory function of the pancreas and the processes of parietal digestion in broilers. This has a negative effect on feed conversion and average daily weight gain, which leads to a decrease in poultry farming efficiency.

Muradyan Ekaterina A., Revyakin Artem O., Sycheva Irina N.

1. Ablayeva E. A., Kavtarashvili A. Sh., Makhatov B. M., Bupebayeva L. K. Study of the effectiveness of the anti-stress preparation "hydro Rex vital" in broiler chicken production during the winter period. Korkyt Ata Kyzylorda State University, 2025;75;4:109–118. doi: 10.52081/bkaku.2025.v75.i4.289. EDN KGPDYZ.
2. Muradyan E. A., Revyakin A. O. The effect of ascorbic acid supplementation on the antioxidant system status and productive performance of Smena 9 broiler chickens under stress conditions. Vestnik Buryatskoi gosudarstvennoi sel'skokhozyaistvennoi akademii, 2026;1(82):147–153. doi: 10.34655/bgsha.2026.82.1.017. EDN JSPHJN (in Russ.).
3. Muradyan E. A., Makaeva V. I. Indicators of stress resistance in broiler chickens using stress-protective drugs. Timiryazevskii biologicheskii zhurnal, 2024,2:86–90. doi: 10.26897/2949-4710-2024-2-2-86-90. EDN AEUYZT (in Russ.).
4. Kavtarashvili A. Sh., Kolokolnikova T. N. Physiology and productivity of poultry under stress (review). Sel'skokhozyaistvennaya biologiya, 2010;45;4:25–37. EDN MUKCUF (in Russ.).
5. Hirakawa R., Nurjanah S., Furukawa K., Murai A., Kikusato M., Nochi T. [et al.]. Heat stress causes immune abnormalities via massive damage to effect proliferation and differentiation of lymphocytes in broiler chickens. Frontiers in Veterinary Science, 2020;7:46. doi: 10.3389/fvets.2020.00046.
6. Musa A. A., Mamat-Hamidi K., Idrus Z., Chung E. L. T., Samat N., Kassim N. A. Effects of heat stress on growth metrics, carcass characteristics, telomere length, and gene expression in chickens. Poultry Science, 2025;104;11:105698. doi: 10.1016/j.psj.2025.105698.
7. Bukaeva Yu. G., Mishurova M. N. The mechanism of the influence of stress on poultry productivity. Proceedings from Priority scientific research and innovative technologies in the agro-industrial complex: science to production: Natsional'naya nauchno-prakticheskaya konferentsiya. (PP. 423–427), Volgograd, Volgogradskii gosudarstvennyi agrarnyi universitet, 2019 EDN OOIOMM (in Russ.).
8. Ghaleghafi A., Khorshidi K. J., Jafari M. A. Nutritional and managerial interventions on growth performance, nutrient transport-related genes and behavioral responses in heat stressed broiler chickens. Veterinary and Animal Science, 2025;31:100561. doi: 10.1016/j.vas.2025.100561.
9. Sugiharto S. Dietary strategies to alleviate high-stocking-density-induced stress in broiler chickens – a comprehensive review. Archives Animal Breeding, 2022;65;1:21–36. doi: 10.5194/aab-65-21-2022.
10. Mirzarakhimova M. A., Kadyrov Sh. K. Enzyme homeostasis and secretion of pancreatic enzymes in rats under the combined influence of hypokinesia, high temperature and insolation. Molodoi uchenyi, 2018,5(191):52–55. EDN YNTGPU (in Russ.).
11. Polyakova E. P., Makashova T. A., Metreveli T. V., Revyakin A. O. Alkaline phosphatase activity in the parietal and luminal mucus of different parts of the intestine in mini-pigs of the Svetlogorsk breed. Biomeditsina, 2014;4:80–84. EDN TVVMQF (in Russ.).
12. Horiguchi M., Sunaga K. Effects of glucocorticoids, cold exposure and irregular feeding on hepatic and pancreatic enzyme activities in mice. Journal of Japan Society of Nursing Research, 1993;16;3:3_11–3_21. doi: 10.15065/jjsnr.19930701001.
13. Vertiprakhov V. G., Fisinin V. I., Egorov I. A., Grozina A. A., Lenkova T. N., Manukyan V. A. [et al.]. Activity of digestive enzymes in duodenal chyme and blood plasma in original lines and hybrids of meat chickens when using biologically active additives in the diet. Sel'skokhozyaistvennaya biologiya, 2017;52;6:1226–1233. doi: 10.15389/agrobiology.2017.6.1226rus. EDN YLSVFO (in Russ.).
14. Han M., Chen B., Dong Y., Miao Z., Su Y., Liu C. [et al.]. Evaluation of liquid organic acids on the performance, chyme pH, nutrient utilization, and gut microbiota in broilers under high stocking density. Animals, 2023;13;2:257. doi: 10.3390/ani13020257.
15. Akinyemi F., Adewole D. Effects of brown seaweed products on growth performance, plasma biochemistry, immune response, and antioxidant capacity of broiler chickens challenged with heat stress. Poultry Science, 2022;101;12:102215. doi: 10.1016/j.psj.2022.102215.
16. Olayiwola S. F., Adedokun S. A. Heat stress in poultry: the role of nutritional supplements in alleviating heat stress and enhancing gut health in poultry. Frontiers in Veterinary Science, 2025;12:1691532. doi: 10.3389/fvets.2025.1691532.
17. Fedorova A. O., Kukharenko N. S., Trush N. V., Gavrilov Yu. A., Gavrilova G. A. The influence of transport disease on the clinical status and some productive qualities of farm animals. Dal'nevostochnyi agrarnyi vestnik, 2023;17;4:111–121. doi: 10.22450/1999-6837-2023-17-4-111-121. EDN KDAYGR (in Russ.).