Biometeorological and Molecular Innovative Study for Modelling and Assessing the Impact of Heat Stress on Water Buffalo Dairy Production: Promising Adaptive Strategies to Cope with Climate Change in Egypt

Background Growing global warming significantly challenges buffalo dairy production, particularly in subtropical climates where summer heat exceeds their thermal comfort zone. Since 2014, Egypt's buffalo milk production has declined. However, few studies have addressed interventions to alleviate the underlying causes. This study proposed a short-term adaptation strategy based on enhancing environment and management practices to alleviate the impact of heat stress (HS) on the physiological and production performance of 12 lactating Egyptian buffaloes (Bubalus bubalis) over 47 summer days in Mit Helfa, Egypt. Meteorological data were monitored daily, and temperature humidity index (THI) was calculated. The daily milk yield (DMY) was recorded alongside the rectal temperature (RT) and respiratory rate (RR). Milk samples were also collected for molecular, biochemical, and quality assessments. Results Two HS models were defined based on THI data. HS Model I (Group A) represented the critical, severe, and moderate HS zones (CHSZ, SHSZ, and MHSZ). Meanwhile, the HS Model II (modified, Group B) reflects the modulatory effects of adaptive interventions in reducing the THI and remodelling the CHSZ and SHSZ to non-HS zones (NHSZ). Additionally, this study provides the first transcriptional analysis of energy homeostasis genes in water buffaloes. It revealed significantly higher expression levels of AMPK, HRH1, and mTOR genes in the HS-Gp A compared to non-HS Gp B (p>0.05). Production data revealed a significant 53% increase in DMY (13 kg/day) in Gp B with lower oxidative stress and superior milk quality. Correlation and regression statistics indicated that higher THI increased RT and RR and significantly decreased DMY in HS Gp A. Conversely, lower THI in Gp B reduced physiological stress and significantly increased DMY (p>0.001). For each unit increase in THI above 69, the DMY decreases by 0.17 and 0.23 kg/day/buffalo, with total predicted decreases of 1.9 and 2.5 kg when the THI increases from 70 to 83 and 65 to 76 (maximum and minimum THI) in HS and Non-HS groups, respectively. Conclusion These findings highlight the negative impact of HS on buffalo health and productivity, emphasising the need for adaptive strategies and genetic research to maintain energy balance, support milk production, and develop heat-tolerant breeds.