Heat stress in dairy cattle in the Volga Federal District of the Russian Federation: myth or reality (a retrospective analysis from 1970 to 2024)

Relevance. Heat stress significantly influences the physiological state of dairy cattle, affecting their milk yield and milk quality. Various techniques exist for assessing heat stress in dairy cattle based on meteorological parameter values.

Methods. A retrospective analysis was performed on climate data arrays collected at weather stations in regions belonging to the Volga Federal District over the period from 1970 to 2024. The values of the temperature and humidity index (THI) and the equivalent temperature index (ETI) were calculated, the comfort of environmental conditions was assessed, and the severity of thermal stress was determined.

Results. In the Volga Federal District, on average, 16.24% of THI values indicated thermal stress in dairy cattle, with the majority (12.38%) categorized as moderate heat stress by severity. The maximum proportions of TVI values characteristic of heat stress were found in the Orenburg and Saratov regions (27.49% and 27.44%), the minimum — in the Perm Region (9.87%). Variability in regional ranking was noted depending on the chosen THI calculation methodology. The most frequent occurrence of THI corresponding to moderate-level heat stress was registered in Orenburg region (19.96%), with the least occurring in Perm Krai (7.85%). The average ETI index representing heat stress among Volga Federal District entities was 14.82%, reaching up to 19.69% in Penza region and down to 10.94% in Perm Krai.

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