Acute heat stress (AHS) is known to affect rabbit production and well-being negatively. Yet, early acute heat stress effect on later physiological response is poorly studied. Our study aimed to provide more knowledge of rabbit physiological response to early acute heat stress in two distinguished rabbit breeds. A total of 120 males of New Zealand White (NZW) and Baladi Black (BB) rabbits five weeks old were recruited and randomly divided into two sub-groups, control groups (Control) reared in a controlled environmental chamber 28
C, and 40% RH and early acute heat stress groups (HS) exposed to 36
C and 62% RH for 6 hours. At 13weeks, rabbits of all groups were subjected to the same AHS conditions. Our results, irrespective of breeding dif- ferences, demonstrate a significant ( <.05) increase in inflammation markers (TNFa, IL-6 and lipid peroxidation), acute-phase proteins (ceruloplasmin, a-1-acid glycoprotein), and DNA frag- mentation with a significant reduction in liver antioxidant enzymes concentrations (glutathione reduced, superoxide dismutase, and catalase) in HS groups compared to breed relative control groups. Furthermore, when all experimental groups at 13weeks of age were subjected to the same stress conditions, the early HS group showed the same significant adverse physiological effects. It can be suggested that rabbits from different genetic groups are vulnerable to acute heat stress exposure at the early stage of life compared to later stages