Abstract
Heat stress typically causes substantial financial losses because it lowers animal performance, morbidity, and mortality. It is essential to comprehend the physiological reactions and biochemical alterations through different body homeostasis during various environmental seasons to prevent harmful impacts of heat stress. Objective of this experiment was to evaluate the different seasonal dynamics of the Egyptian buffaloes' oxidative, hormonal, metabolic and physiological responses to the country's summer season climate. Throughout the year, the physiological reactions of twenty lactating water buffaloes were measured. These responses included rectal temperature (RT), respiration rate (RR) and body surface temperature (BST), in addition to serum hormonal, oxidative/antioxidant, and metabolic indices. Significant increases in RR and BST were detected in summer season in relation to winter season when the temperature-humidity index (THI) was higher (>80). The heat stress during the summer season was associated with lower serum antioxidant enzyme levels and higher oxidative stress. Serum cortisol and hepato-renal functional bio-indicators were also significantly elevated in the summer and autumn. In comparison to former seasons, the levels of growth hormone (GH), triiodothyronine (T3), thyroxine (T4), and adrenocorticotrophic hormone (ACTH) were also much reduced in the autumn and summer. THI was found to have a negative relation with physiological and antioxidant indices, but a positive relation with serum cortisol and malondialdahyde (MDA) levels. According to our findings, lactating Egyptian buffaloes have considerable heat stress during the summer season, which necessitates greater managerial measures to prevent animal welfare concerns and economic losses.

Key words: Buffalo, Heat stress, Physiological response, Oxidative stress, Temperature–humidity index