Impact of Heat Stress on Productivity and Health in Holstein Dairy Cows
Bexeitov T. Akhazhanov E. Akhazhanov K. Kainidenov N. Jaxybayeva G.
November-December 2026Unique Scientific Publishers
International Journal of Veterinary Science
2025#14Issue 61372 - 1379 pp.
Heat stress, one of the prominent problems in dairy farming, poses a significant threat to dairy production, particularly for high-yielding breeds like Holstein in continental climates such as Kazakhstan. This study comprehensively assessed the impact of heat stress on 90 lactating Holstein cows in Kazakhstan, stratified by stress resistance (high, medium, low) based on baseline blood cortisol levels. Behavioral, physiological, and productivity parameters were also evaluated during a thermoneutral period (May, 16-21℃ average daytime temperature, and 65% humidity) and a heat stress period (June, 22-35℃ average daytime temperature, and 60% humidity). Under heat stress, all groups exhibited reduced feed intake (ranging from 2.1 to 3.4kg/day, P<0.01) and milk yield (ranging from 2.18 to 2.26L, P<0.01). Cows with high stress resistance were the most sensitive physiologically, showing significant decreases in blood calcium (2.16 vs. 2.10mmol/L, P<0.01), phosphorus (2.34 vs. 2.04mmol/L, P<0.01), and mean corpuscular hemoglobin (14.73 vs. 14.27pg, P<0.05). Despite a greater physiological response, the high-resistance group maintained the highest absolute milk production (27.13L vs. 24.87L and 23.13L in the medium and low groups, respectively). The results indicate that blood cortisol is an effective biomarker for stratification and that selecting for high stress-resistant cows, despite their acute physiological sensitivity, is a promising strategy to mitigate production losses in dairy herds exposed to heat stress.
Biomarkers , Cortisol , Heat stress , Holstein cows , Milk productivity , Stress tolerance
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Research Institute of Agroinnovation and Biotechnology, NAO Toraigyrov University, Pavlodar, 140000, Kazakhstan
K.I. Skryabin Moscow State Academy of Veterinary Medicine and Biotechnology-MVA, Moscow, 109472, Russian Federation
Federal State Budgetary Institution of Science Institute of General Genetics named after N.I. Vavilov, Russian Academy of Sciences, Moscow, 119991, Russian Federation
Research Institute of Agroinnovation and Biotechnology
K.I. Skryabin Moscow State Academy of Veterinary Medicine and Biotechnology-MVA
Federal State Budgetary Institution of Science Institute of General Genetics named after N.I. Vavilov
10 лет помогаем публиковать статьи Международный издатель
Книга Публикация научной статьи Волощук 2026 Book Publication of a scientific article 2026