Impact of absorbed dose on the health status of lactating cows in the Bryansk region: comprehensive analysis of blood parameters in the long-term post-Chernobyl period

The aim of this study was to assess the impact of the absorbed dose from chronic incorporated irradiation by 137Cs on the hematological and biochemical parameters of blood in lactating cows during the long-term period after the Chernobyl accident. The study was conducted on 14 animals se-lected from two farms in the Bryansk region. These farms are located on radioactively contaminated territories within the zone of residence with the right to resettlement, where the current soil contamination density of 137Cs is 185-555 kBq/m2 (5-15 Ci/km2). The study was carried out during the pasture period of 2023-2024. An assessment of the radiological conditions for keeping the study animals on the farms was performed. The whole-body absorbed dose from internal and external chronic expo-sure to 137Cs was 0.57-1.72 mGy/y, which is significantly below the threshold for deterministic effects from acute external exposure. The complete blood count parameters corresponded to the physiolog-ical norm and were distributed within the reference values. Biochemical blood analysis showed a statistically significant decrease in urea levels in both experimental groups (2.77-2.85 mmol/L), as well as a decrease in total calcium (2.07 mmol/L) and inorganic phosphorus (1.05 mmol/L) levels in one experimental group. This may indicate pathological or compensatory processes occurring in the animals' bodies due to chronic incorporated irradiation during the long-term period of the conse-quences of radioactive contamination. The identified metabolic disorders have been confirmed by biochemical blood analyses conducted by veterinary laboratories from 2013 to 2025 and may be caused by the impact of ionizing radiation on both the macroorganism and the gastrointestinal tract microflora. The pathophysiological mechanism could be associated with a number of factors: altered protein metabolism, impaired liver function, suppression of ruminal fermentation, chronic exposure of radionuclides to the gastrointestinal mucosa, disrupted mineral metabolism and its hormonal regula-tion. These factors negatively affect animal health status.